The escalation comes as Lebanon and Israel prepare for talks between military delegations at the Pentagon on Friday, and for US-brokered talks early next week -- the fourth round since the latest Israel-Hezbollah war erupted on March 2.

After heavy strikes earlier Thursday that Lebanese authorities said killed at least 14 people including three children, Israel's military said it "precisely struck in Beirut", without identifying the target.

The Lebanese military source told AFP on condition of anonymity that "an Israeli strike targeted an apartment in the Choueifat area".

AFPTV footage showed smoke rising from the area on the edge of Beirut's southern suburbs, a Hezbollah stronghold.

It is the second Israeli strike on south Beirut since a ceasefire between Israel and the Iran-backed Hezbollah that was supposed to have taken effect on April 17 but has never been observed.

Both sides accuse each other of violating it and justify their attacks by the other camp's alleged breaches of the truce.

Hezbollah on Thursday claimed several attacks with rockets and drones on Israeli troops in south Lebanon.

- 'History and civilisation' -

On Wednesday, Israel's military declared all areas south of Lebanon's Zahrani River -- an area roughly 40 kilometres (25 miles) from the border and including the major cities of Tyre and Nabatieh -- as "combat zones" and told residents to evacuate ahead of attacks against Hezbollah.

Earlier this week, Israel vowed to ramp up operations in Lebanon and said it was expanding ground operations there.

A series of Israeli airstrikes early Thursday hit the coastal cities of Tyre and Sidon, AFP correspondents said.

Lebanon's civil defence agency told AFP that eight strikes had hit Tyre since Wednesday evening, in addition to others on the city's outskirts, after Israel issued evacuation warnings to residents.

The state-run National News Agency (NNA) said several buildings, a cafe and a motorcycle were among the targets.

AFP footage early Thursday showed a fireball followed by a cloud of smoke as a strike hit a building in Tyre's archaeological district.

Ghazouane Halawani, who lives near a building hit by a strike, told AFP that he believed Israel wanted to attack the ancient city's "history and its civilisation".

"We're staying here. This is our country, our land, our life," he added.

Lebanon's health ministry said one strike in Tyre killed two Syrians including a child.

- Israeli soldier killed -

The ministry said another strike hit a building in the city of Sidon, killing five people, including two women, and wounded 21, five of them children.

An AFP correspondent said the raid destroyed the first two floors of a residential building.

The health ministry said another strike hit a vehicle in Adloun, in the Sidon district, killing six people "including two children, their mother and their father".

The Lebanese military said a soldier was killed in an Israeli strike "while he was driving on the road" in the Nabatieh region.

The NNA also reported Israeli strikes in other areas of the country's south.

The Israeli military said a soldier was killed on Wednesday by a Hezbollah drone near the border, with 24 Israelis now killed since the hostilities began in March, including 23 soldiers and one civilian contractor.

Lebanon was drawn into the Middle East war when Hezbollah launched rockets at Israel in retaliation for the killing of Iran's supreme leader in US-Israeli attacks, prompting Israeli strikes and a ground invasion.

As expectations rose recently of a possible understanding between Tehran and Washington to end the broader conflict, Iran has insisted any agreement must apply to Lebanon.

But on Thursday, the United States and Iran accused each other of violating their ongoing truce following an exchange of fire.