Israeli forces fired on two positions used by United Nations peacekeepers in southern Lebanon on Thursday and at another one on Wednesday, the UN said, as Israel pressed its assault on Hezbollah and told Lebanese civilians not to return to homes in the south.

The UNIFIL force said two of its peacekeepers were injured in one of the incidents, when an Israeli tank fired at an observation tower at the force's main headquarters in Naqoura, hitting the tower and causing the peacekeepers to fall. There were no casualties in the other two incidents, a UN source said.

"Any deliberate attack on peacekeepers is a grave violation of international humanitarian law," UNIFIL said in a statement, adding that it was following up with the Israeli military.

There was no immediate comment from the Israeli military, which is waging a widening offensive in Lebanon against the Iran-backed Hezbollah movement.

Lebanon's caretaker prime minister, Najib Mikati, said contacts were underway between the United States and France with the aim of reviving a ceasefire, an apparent reference to diplomatic efforts to clinch a truce that Israel rejected last month. There was no immediate comment from Washington or Paris.

The Middle East remained on high alert for further escalation of the conflict that has swept through the region since the Hamas-led attacks on Israel a year ago, awaiting Israel's response to an Iranian missile strike last week.

Biden and Netanyahu speak

U.S. President Joe Biden and Israeli Prime Minister Benjamin Netanyahu spoke on Wednesday about potential Israeli retaliation against Iran, in a call both sides described as positive.

Israel says its Lebanon offensive aims to secure the return home of tens of thousands of Israelis who evacuated northern Israel due to cross-border rockets launched by Hezbollah, which opened fire a year ago to support Hamas in Gaza.

WATCH | Canada pledges humanitarian support: 

Federal government announces $15M for humanitarian assistance in Lebanon

International Development Minister Ahmed Hussen says the additional federal money will go towards food, water, emergency health services and protection services for those who need it most in Lebanon.

The UNIFIL peacekeeping force in Lebanon was established in 1978 and expanded following a 2006 war between Israel and Hezbollah. It has around 10,500 personnel, with major contributing nations including France, Italy, Indonesia, Malaysia and Ghana, according to UNIFIL's website.

UNIFIL said Israeli soldiers had also fired at a UN position in Ras Naqoura, "hitting the entrance to the bunker where peacekeepers were sheltering, and damaging vehicles and a communications system."

"An IDF drone was observed flying inside the UN position up to the bunker entrance," UNIFIL said. The previous day, Israeli forces had "fired at and disabled the position's perimeter-monitoring cameras," it added. They also deliberately fired at and damaged another position, it said.

No comment from Israeli military

The Lebanese health ministry said an Israeli strike overnight hit a civil defence centre in the village of Derdghaiya, some 10 kilometres from the border, killing five paramedics and rescue workers.

There was no immediate comment from the Israeli military.

Israeli strikes have killed more than 2,100 people in Lebanon over the last year, the vast majority of them since Sept. 23, when Israel dramatically scaled up its assault with widespread airstrikes before later sending soldiers in on the ground. The toll does not distinguish between civilians and combatants.

Hezbollah cross-border fire at Israel has killed 53 people, more than half of them civilians.