Israel's air force carried out an airstrike on the Choueifat area on the edge of Beirut's southern suburbs on Thursday afternoon, the Israeli military said, further straining a fragile ceasefire a day ahead of crucial negotiations in Washington.

The strike hit an apartment building. Videos from Choueifat, close to Beirut's international airport, showed white smoke billowing from a residential neighborhood.

Five people were killed and 21 others wounded overnight when an Israeli drone struck an apartment building in the southern city of Sidon where some displaced families lived, the first such attack on Sidon during the latest escalation.

The attack likely came in response to a drone attack that killed a female Israeli soldier in north Israel. LBCI television had reported that Israel had informed the U.S. of its intention for escalation after the attack.

The Israeli military said on Wednesday that all areas south of Lebanon's Zahrani River, which runs roughly 40 kilometers (25 miles) north of the Israel-Lebanon border, were considered "combat zones" and urged residents to head north.

The Israeli military said on Thursday it had begun new strikes on Hezbollah infrastructure around the southern Lebanese city of Tyre after issuing an evacuation warning to its residents.

The Israeli military said on Thursday that a soldier was killed the day before by a Hezbollah drone near the Lebanon border, taking to 24 the number of its troops killed in the war with the Iran-backed group.

The reason the Israeli army has not carried out an attack in Beirut and its southern suburbs despite the latest escalation is an "American veto," unnamed sources told Israeli newspaper Yedioth Ahronoth on Wednesday.

Hezbollah said its fighters clashed with Israeli forces in a town north of the Litani river on Wednesday, a day after Israel's military said it was expanding its ground operations in the country's south.

Israeli strikes on southern Lebanon killed 31 people on Tuesday, the Lebanese health ministry said, as Israel said it was intensifying attacks despite a truce in its war with Hezbollah.

Israeli forces have begun operating beyond their so-called "Yellow Line" in south Lebanon, which runs around 10 kilometers (six miles) deep inside Lebanese territory, a military official confirmed to AFP on Tuesday.

The health ministry said Tuesday that an Israeli strike a day earlier killed at least 11 people, two of them children, as the Israeli military said it had launched strikes on Hezbollah infrastructure.

In a statement, the ministry said that "yesterday's Israeli enemy airstrike on the town of Mashghara in West Bekaa resulted in a preliminary toll of 11 martyrs, including two girls and a woman, and 15 wounded, including a child", adding that rescuers were still clearing the rubble in the eastern town.