At least three Lebanese soldiers and one Israeli soldier have been killed during a skirmish along the border between the two countries.
We'll be live-blogging the latest developments from both Israel and Lebanon throughout the day. (All times are GMT, except where noted.)
9:00pm: That's all for the live-blogging this evening! But we'll obviously continue to follow this story on the main Al Jazeera Web site in the hours and days to come.
8:15pm: A few other odds and ends we missed earlier today.
First, Binyamin Netanyahu, the Israeli prime minister, echoed what we've heard from other Israeli officials (including foreign minister Avigdor Lieberman). He called the skirmish a violation of UN resolution 1701, and said the Lebanesse government was "directly responsible."
Several other countries, including Iran and Jordan, offered their reactions throughout the day. We've rounded them up here.
And the United Nations promised to announce the results of its investigation into the skirmish at a press conference on Wednesday.
Major General Alberto Asarta Cuevas, the head of the UN peacekeeping force in Lebanon, has been in New York for the last few days meeting with senior UN officials he is now on his way back to Lebanon.
7:03pm: Avital Liebovich, a spokeswoman for the Israeli military, was on Al Jazeera a little while ago talking about the attack. She called it a "pre-planned" attack and accused the Lebanese army of positioning snipers in the area.
We coordinated this operation with Unifil. It was not done in a secret manner. We have reason to believe this attack was pre-planned by the Lebanese army.
Liebovich did not provide any evidence to back up that claim, though, nor has the Israeli military.
6:46pm: Two other items from Nasrallah's (still-ongoing) speech. First, he threatened to retaliate against Israel for any "future aggression."
The Israeli hand that targets the Lebanese army will be cut off.
He also attacked Israel on several other issues: He accused it once again of running a large spy ring in Lebanon, and said more than 100 spies have been arrested in the last two years and he accused it of trying to use the UN Special Tribunal for Lebanon, which is investigating the assassination of Rafiq al-Hariri, to create divisions in Lebanon.
6:18pm: Hezbollah chief Hassan Nasrallah is speaking right now in front of a large crowd in Beirut (Nasrallah, as usual, is not actually at the rally he's delivering his speech via video).
Hezbollah was not involved in the skirmish today. They also haven't said anything about the incident until now - presumably because the group didn't want to preempt Nasrallah's speech, which was already scheduled for this evening.
Nasrallah said that Hezbollah would put itself "at the disposal" of the Lebanese army, which he praised for its bravery.
We were immediately at a high state of alert... but the national interest demanded that the Lebanese resistance put itself at the disposal of the army.
We called the president, the parliament speaker and the prime minister, and we said, we will not take any action [unilaterally], despite the great pain we felt.
5:45pm: PJ Crowley, the US state department spokesman, urged "maximum restraint" from both sides, and said the US was in touch with both the Israeli and Lebanese governments.
We are trying to understand what happened... our greatest concern is that whatever did happen not be repeated. The region has enough tension as it is. The last thing that we want to see is that this incident expand into something more significant.
4:51pm: Lebanon's higher defence council just wrapped up the emergency meeting called by president Michel Sleiman.
“After consultations, the council has ... given instructions to face all aggressions on our territory, army and people by all available means, no matter the sacrifices,” said General Said Eid, the head of the council.
4:44pm: The United Nations Security Council just wrapped up a brief closed-door meeting on Israel and Lebanon.
Alain Le Roy, the head of UN peacekeeping operations, said the UN is still investigating the incident, and that he'll have more details tomorrow. The Security Council didn't issue any formal statement on today's skirmish.
3:45pm: The Israeli army just confirmed that another officer - a captain - was wounded in the fighting today.
To recap the casualty figures, then: Three Lebanese soldiers were killed, and four wounded one Israeli soldier was killed, and one wounded and a Lebanese journalist was killed.
3:20pm: Selim el-Sayegh, Lebanon's minister of social affairs (and a member of the Phalange party), told Al Jazeera that he didn't believe the Lebanese army instigated the fighting (as the Israeli government has alleged).
The history of the Lebanese army's actions have been defensive... it is in no position whatsoever to conduct any attack against Israel. It wants only to defend Lebanese territory... Israel has been doing these activities as a matter of provocation.
3:08pm: The Israeli army has confirmed that a lieutenant colonel was killed during the skirmish today.
2:43pm: General Gadi Eisenkot, the head of Israel's northern command, just called the clashes a "one-time event," and said he didn't expect the violence to escalate.
He also said two Israeli officers were wounded in the fighting.
2:24pm: As we mentioned in a story yesterday: The International Crisis Group has a timely new report out called Drums of War, assessing the possibility of another conflict between Israel and Lebanon. Their summary of the situation:
Four years after the last war, the situation in the Levant is paradoxical. It is exceptionally quiet and uniquely dangerous, both for the same reason. The build-up in military forces and threats of an all-out war that would spare neither civilians nor civilian infrastructure, together with the worrisome prospect of its regionalisation, are effectively deterring all sides. Today, none of the parties can soberly contemplate the prospect of a conflict that would be uncontrolled, unprecedented and unscripted.
1:54pm: NOW Lebanon is reporting that Sleiman has called for an emergency session of Lebanon's higher defence council.
Smoke rises above the village of Adaisseh [AFP]
1:43pm: Syria's state-run SANA news agency released a summary (in Arabic) of Bashar al-Assad's phone call with Sleiman.
President Bashar al-Assad telephoned Lebanese president Michel Sleiman on Tuesday and expressed Syria's support for Lebanon against the brazen aggression launched by Israel.
Assad believes that this aggression proves once more that Israel has always sought to destabilise security and stability in Lebanon and the region.
1:33pm: Al Jazeera just spoke with Neeraj Singh, a spokesman for UNIFIL, who said that peacekeepers are being deployed in the area.
We are focused on restoring calm in the area... UNIFIL peacekeepers are deployed in the area, and our immediate priority right now is to restore calm.
1:24pm: A few regional reactions. Bashar al-Assad, the Syrian president, phoned Sleiman and told him Syria "stands with Lebanon."
And Ahmed Aboul Gheit, the Egyptian foreign minister, spoke with Hariri and promised Egyptian support. He also called for "self-restraint," and asked the UN to intervene to "de-escalate" the situation.
1:14pm: Many reports say this whole incident started because Israeli troops were trying to cut down a tree on the Lebanese side of the border.
The US television network MSNBC has posted a photograph that appears to show an Israeli soldier, in a crane, cutting down a tree on the Lebanese side of the border fence.
1:08pm: The Israeli military, which issued only a brief statement this morning on the clashes, just e-mailed a longer statement to reporters.
It claims an Israeli army unit was carrying out "routine maintenance" along the border, and that the work was "pre-coordinated" with UNIFIL, the United Nations peacekeeping force in the region.
The IDF force immediately returned fire with light arms at a force of the LAF, and the IDF also made use of artillery fire.
[...] The IDF holds the LAF responsible for the incident that disrupted the calm in the region, and its consequences.
12:56pm: Israeli foreign minister Avigdor Lieberman, meanwhile, said Israel "holds the Lebanese government responsible" for the incident.
This recent violation is one of many violations of Resolution 1701, the most severe of which is the massive rearmament of Hizbullah, including the rearmament of Hizbullah units in southern Lebanon.
He also directed the Israeli representative at the United Nations to file a formal complaint about Lebanon.
12:51pm: Saad Hariri, the Lebanese prime minister, and Michel Sleiman, the Lebanese president, were the first two senior Lebanese politicians to comment on the clash.
UN peacekeepers wave flags at Israeli troops [AFP]
Hariri's statement was predictable: It condemned Israel's "violation of Lebanese sovereignty" and demanded that the UN stop the fighting.
Sleiman said much the same thing, but he also included a message for the Lebanese army, asking it to "confront any Israeli aggression, whatever the sacrifices."
12:45pm: There are many conflicting reports from southern Lebanon, but the latest confirmed details right now (from the Lebanese defence ministry) are that three Lebanese soldiers were killed, and four others wounded.
There are also reports of an Israeli soldier killed in the fighting - the Al-Manar television station, which is run by Hezbollah, has carried that story for an hour or so - but no confirmation from the Israeli military.
A journalist was also killed in the fighting Lebanese media are identifying him as Assaf Abou Rahhal, from the Al-Akhbar newspaper.