U.S. and Arab mediators are working round-the-clock to hammer out a ceasefire deal between Israel and Hamas, sources close to the talks said, while in the Gaza Strip medics said Israeli strikes had killed 13 Palestinians on Thursday.

Mediators had managed to narrow some gaps on previous sticking points but differences remained, the sources said.

In Gaza, medics said at least 13 Palestinians were killed overnight in separate Israeli airstrikes, including on two houses in Gaza City and a central camp.

Residents of Jabalia in the northern Gaza Strip, where the army has operated since October, said forces blew up clusters of houses overnight.

"The longer those talks last, the more destruction and death takes place in Gaza. Jabalia, Beit Hanoun, and Beit Lahiya are being wiped out, Rafah too," said Adel, 60, a resident of Jabalia, who is now displaced in Gaza City.

Palestinians accuse Israel of ethnic cleansing in those areas by depopulating residents to create buffer zones.