An Israeli airstrike killed four people including a Hezbollah official in Beirut's southern suburbs on Tuesday, a Lebanese security source said, further testing a shaky ceasefire between Israel and Iran-backed Hezbollah.

The Israeli military said the official - Hassan Bdeir - was a member of a Hezbollah unit and Iran's Quds Force, and he had assisted the Palestinian group Hamas in planning a "significant and imminent terror attack against Israeli civilians".

Hezbollah confirmed that Bdeir had been killed along with his son, who was also a member of the group. The Lebanese security source said Bdeir was a mid-ranking commander whose responsibilities included the Palestinian file.

The Lebanese health ministry said the strike killed four people - including a woman - and wounded seven others.

It marked Israel's second airstrike in the Hezbollah-controlled suburb of Beirut in five days, adding to strains on the US-brokered ceasefire that ended last year's devastating conflict.

The attacks on Beirut's southern suburbs have resumed at a time of broader escalation in the region, with Israel having restarted Gaza strikes after a two-month truce and the United States hitting the Iran-aligned Houthis of Yemen in a bid to get them to stop attacking Red Sea shipping.

Hezbollah lawmaker Ibrahim Moussawi said the Israeli attack amounted to "a major and severe aggression that has escalated the situation to an entirely different level".

Speaking in a televised statement after visiting the building that was struck, he called on the Lebanese state to "activate the highest level of diplomacy to find solutions".

Israeli Foreign Minister Gideon Saar said the eliminated Hezbollah operative posed "a real and immediate threat". "We expect Lebanon to take action to uproot terrorist organizations acting within its borders against Israel," he said.

Israel dealt severe blows to Hezbollah in the war, killing thousands of its fighters, destroying much of its arsenal and eliminating its top leadership, including Hassan Nasrallah.

Hezbollah has denied any role in recent rocket attacks from Lebanon towards Israel, including one that prompted Israel to carry out an airstrike on the southern suburbs last Friday.

Tuesday's strike in the early hours appeared to have damaged the upper three floors of a building, a Reuters reporter at the scene said, with the balconies of those floors blown out.

The glass on the floors below was intact, indicating a targeted strike. Ambulances were at the scene as families fled to other parts of Beirut.