A ceasefire between Israel and Palestinian militants in the Gaza Strip appears to be holding.

The Egypt-brokered truce followed three days of violence with Israel targeting the Palestinian Islamic Jihad (PIJ) and militants firing rockets into Israel.

At least 44 Palestinians died in the most serious flare-up since an 11-day conflict in May 2021.

On Monday, Israel began lifting its blockade of the Strip, allowing the first fuel tanks to enter.

The latest violence began with attacks by Israel on sites in the Gaza Strip, which its military said was in response to threats from a militant group. It followed days of tensions after Israel arrested a senior PIJ member in the occupied West Bank.

By Sunday evening, the Palestinian health ministry said that 15 children had been confirmed among the 44 deaths recorded.

Gaza's health ministry has blamed "Israeli aggression" for the deaths of Palestinians and for the more than 300 people wounded.

Israel, for its part, says it hit 170 PIJ targets during the operation, codenamed Breaking Dawn, killing several high-ranking PIJ members and destroying tunnels and weapon storage sites.

A spokesman for the Israel Defense Forces (IDF) said they had information about 35 Palestinian deaths: "11 of them were uninvolved civilian casualties, including the wives of the terror group's commanders in the south - victims of the IDF attacks."

"Another 15 civilians were killed by PIJ fire," Brig Gen Ran Kochav said.

Gen Kochav said 1,100 projectiles were fired from the Gaza Strip during the flare-up, with 200 landing inside Gaza.

He said more Palestinians had died from those rockets that exploded inside the Strip than from IDF fire, and added that Israel would investigate the deaths of civilians, including children.

No Israeli casualties have been reported, with the exception of a few people lightly injured from debris on Saturday.

The ceasefire was mediated by Egypt, which has acted as an intermediary between Israel and Gaza in the past.

But as it came into effect late on Sunday, the Israeli military confirmed it was striking Palestinian Islamic Jihad (PIJ) targets in Gaza, in response to rockets fired just before.

Israeli media also reported some isolated rocket fire from Gaza in the minutes after the deadline.

US and United Nations leaders urged both sides to continue to observe the ceasefire.

In a statement, US President Joe Biden praised the truce and called on all parties "to fully implement [it] and to ensure fuel and humanitarian supplies are flowing into Gaza".

He also urged that reports of civilian casualties should be investigated in a timely manner.

Concerns over the humanitarian situation in Gaza, where health officials warned that hospitals only had enough fuel to run generators for another two days, led to the ceasefire deal being agreed.

As the truce held, restrictions on Gaza began to be lifted.

Humanitarian aid started arriving as the major crossings into the Strip, closed six days ago, were reopened, Israel said.

They would return to "full routine... subject to calm in the area," a statement said.

The latest conflict closely follows Israel's arrest of Bassem Saadi, reported to be the head of PIJ in the West Bank, a week ago.

He was held in the Jenin area as part of a series of arrest operations, after a wave of attacks by Israeli Arabs and Palestinians that left 17 Israelis and two Ukrainians dead. Two of the attackers came from the Jenin district.

Large crowds gathered on Sunday for the funerals of those killed in strikes on Rafah, in the south of the territory. These included senior PIJ commander Khaled Mansour - the second top militant to have died. Demonstrations in support of Gaza have also been held in the West Bank city of Nablus.

PIJ, which is one of the strongest militant groups operating in Gaza, is backed by Iran and has its headquarters in the Syrian capital, Damascus.

It has been responsible for many attacks, including rocket fire and shootings against Israel.

In November 2019, Israel and PIJ fought a five-day conflict following the killing by Israel of a PIJ commander who Israel said had been planning an imminent attack. The violence left 34 Palestinians dead and 111 injured, while 63 Israelis needed medical treatment.

Israel said 25 of the Palestinians killed were militants, including those hit while preparing to launch rockets.