Tension is rising across the Middle East as Israel and Hamas, the Palestinian group which controls the Gaza Strip, continue to exchange fire amid the worst outbreak of violence since the Israeli assault on the territory nearly four years ago.
As the death toll in Gaza reached 19, three Israelis were killed in the southern town of Kiryat Malachi on Thursday after a rocket fired from Gaza hit an apartment building.
Israeli sources said two rockets hit the Tel Aviv area - one landed in the sea while another missile landed in an uninhabited area of Israel's commercial centre.
Air raid sirens sent residents running for shelter in Tel Aviv, a Mediterranean city that has not been hit by a rocket since the 1991 Gulf War.
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Islamic Jihad, another Gaza-based Palestinian group, said that it had fired one of the rockets that hit Tel Aviv.
Late on Thursday, Israel began moving troops towards the Gaza Strip and Ehud Barak, the Israeli defence minister, authorised the call-up of 30,000 reservists for a possible ground operations.
At least a dozen lorries carrying tanks and armoured vehicles were seen moving towards the border area, while buses ferried soldiers.
While southern Israeli areas near Gaza have long coped with rocket fire, the attacks on the Tel Aviv area illustrated the significant capabilities that Hamas has developed.
Palestinian fighters had previously hit Rishon Letzion before but never reached Tel Aviv, which is only 70km north of the Gaza Strip.
At least 19 Palestinians, including two children, have been killed and more than 150 others wounded as of Thursday in fighting which began with an aerial attack that killed Ahmad Jabari, the Hamas military commander who was accused by Israel of overseeing attacks against civilians.
Thursday's deadly rocket fire on Kiryat Malachi was claimed by Jabari's group, the Ezzedine al-Qassam Brigades, in a statement on its website. Jabari's funeral took place in Gaza on Thursday.
"It is important to understand one simple point: there is no moral symmetry between the terrorists in Gaza and Israel," Binyamin Netanyahu, Israeli prime minister, said on Thursday
"They are committing double war crimes," he said. "They fire at Israeli civilians and hide behind Palestinian civilians."
Netanyahu referred to the Israeli attacks on Gaza as "surgical".
Rockets and mortars
On the second day of an assault that Israel said might last many days, its fighter jets bombed targets in and around Gaza City late into the night.
Israel-Gaza conflict intensifies
Israeli authorities said more than 250 rockets and mortars were fired by Hamas and other armed groups from Gaza as of Thursday afternoon, and that its Iron Dome interceptor missile system had shot down dozens of the projectiles.
On either side of the frontier, people fled streets for cover.
Israeli Channel 2 TV showed panicked Tel Aviv residents running for cover and lying down on the ground after the air-raid sirens began sounding.
The armed wing of Islamic Jihad announced on Thursday it had fired an Iranian-built rocket at Tel Aviv.
"The Quds Brigades hit the occupied city of Tel Rabea [Tel Aviv] with a Fajr-5 rocket causing a large explosion to shake the city," the group said in a brief statement, shortly after an AFP correspondent reported seeing a rocket land in the water south of the sprawling coastal city. "What comes next will be greater," it added.
In a separate statement, posted on Islamic Jihad's website, Abu Ahmed, Islamic Jihad spokesperson, pledged that Israel would experience "further surprises so long as the aggression against the Palestinian people continues".
"The enemy began the battle but the resistance will determine how the battle will end," he said.
The sudden conflict pours oil on the fire of a Middle East already tense with two years of revolution and an out-of-control civil war in Syria.
Egypt recalled its ambassador to Israel on Wednesday, summoned the Israeli ambassador to Cairo in protest over the assault and ordered its representative at the UN to call for an emergency Security Council meeting.
Mohamed Morsi, the Egyptian president, spoke to US President Barack Obama and Ban Ki-moon, the UN secretary-general, over the phone and discussed the Gaza escalation with them.
Taher Nuno, Hamas government spokesperson, said that Egypt would send a delegation headed by Hisham Qandil, the Egyptian prime minister, to Gaza on Friday. Israel announced it would cease military activity during Qandil's visit.
Spokesman Mark Regev defends Israeli attacks
Israel warned Hamas that all its men were in its sights and faced censure from influential Arab countries - with the Arab League announcing it would hold an emergency meeting on Saturday.
Mark Regev, spokesperson for Netanyahu's office, told Al Jazeera that Israel will "continue to hit the Hamas military machine, to hit their command and control, to hit their arsenal where they store their weapons".
"Unfortunately, today the Israeli population of southern Israel is on the receiving end of these barrages," he said.
"We have had three people killed. Children, instead of going to school, are stuck in bomb shelters.
"They must understand that they cannot hit Israeli civilians with impunity."
The US has condemned Hamas, long shunned by the West as an obstacle to peace. "There is no justification for the violence that Hamas and other terrorist organisations are employing against the people of Israel," Mark Toner, deputy State Department spokesman, said.
The UN Security Council held an emergency meeting late on Wednesday, but took no action.
In France, Laurent Fabius, foreign minister, said: "It would be a catastrophe if there is an escalation in the region."
"Israel has the right to security but it won't achieve it through violence," he said. "The Palestinians also have the right to a state."
The Ezzedine al-Qassam Brigades issued a communique on Wednesday saying Israel had "opened the gates of hell on itself". Fawzi Barhum, the Hamas spokesman, said Jabari's killing was tantamount to a "declaration of war".