The Israeli army, however, denied on Thursday that the aircraft had struck inside Lebanon, saying attack helicopters opened fire inside Israel's northern border area while searching for what it called two suspected Hizb Allah infiltrators. In other news, Israel has urged the Lebanese government to take action to bring their common border under control.
Witnesses in Lebanon said Israeli helicopters fired two missiles that struck southern Lebanon, while Israeli television said air force jets bombed positions belonging to the Hizb Allah group which was active in the area.
There was no immediate word on casualties.
Israeli media said the air strike came after renewed gun battles on Thursday between Israeli soldiers and Hizb Allah fighters near the border.
The renewed fighting erupted after an Israeli army officer was killed and three soldiers were wounded in an attack in a disputed border zone on Wednesday, in the worst violence in the area in six months.
Hizb Allah was instrumental in ending Israel's 22-year occupation of southern Lebanon in 2000.The two foes have clashed sporadically in the Shebaa farms, a border zone, since then.
Hizb Allah's Hasan Nasr Allah has
vowed to 'liberate' Shebaa Farms
The UN says Israel's withdrawal from Lebanon is complete and Shebaa farms is Israeli-occupied Syrian land.
"The Lebanese government must take responsibility for the Israeli-Lebanese border and prevent terrorist organisations ... from inflaming the situation," the Israeli army said in a statement after Wednesday's attack.
And for the first time since occupation forces withdrew from southern Lebanon, Israeli planes dropped pamphlets into Lebanon between 3.30am and 4am on Thursday.
Aljazeera's correspondent Ghassan bin Jido quoted one flier as saying: "The State of Israel sees that Lebanon's government is responsible for any offensive setting off from its lands against Israel.
"Israel hopes the government takes urgent action to impose its sovereignty on Hizb Allah in southern Lebanon."
Some residents told Aljazeera the drop was a warning message that Israel might escalate military operations in Lebanon's Bekaa Valley, the south and even to the heart of Beirut.
Israel pulled out of south Lebanon in May 2000 after 22 years of occupation but the border remains tense and there have been a number of deadly clashes since the withdrawal.
The small mountainous Shebaa Farms area lies at the convergence of the Israeli, Lebanese and Syrian borders. It was seized by Israel from Syria in the 1967 Middle East war and is now claimed by Lebanon, with Damascus' approval.