Israeli warplanes assassinated three top Hamas commanders in southern Gaza on Thursday, inflicting a heavy blow on the movement's armed wing after failing to kill its top military chief.

As the six-week war between Israel and Hamas raged on leaving truce talks in tatters, a pre-dawn air strike killed three members of the Islamist movement's armed wing, the Ezzedine al-Qassam Brigades.

The Brigades said they were "senior commanders", identifying them as Mohammed Abu Shamala, Raed al-Atar and Mohammed Barhum, and vowed to make Israel pay.

"The assassination... is a big Israeli crime, which will not succeed in breaking our will or weakening our resistance," spokesman Sami Abu Zuhri said.

Israel's Shin Bet internal security agency said Atar and Shamala were among the top five most-wanted Hamas militants.

Defence Minister Moshe Yaalon hailed their deaths as "a big operational and intelligence achievement", and warned that Israel would not hesitate to track down the rest of the group's leaders.

"Hamas leaders should know that we will neither rest nor be silent until we get our hands on them," he said in a statement.

Witnesses said nine missiles blasted the four-storey building in Rafah to smithereens, leaving a huge crater.

Four surrounding buildings had their doors and windows blown out and some outer walls destroyed.

The body of Sabah Yunis, a four-year-old girl, was also pulled from the rubble, emergency services spokesman Ashraf al-Qudra said.

- Abbas meets Meshaal -

The deadly strikes came 36 hours after Israel tried and failed to assassinate Brigades chief Mohammed Deif, who has topped its most wanted list for more than a decade.

That attack levelled a six-storey building in Gaza City, killing two women and three children, among them Deif's wife, his infant son and three-year-old daughter, although he escaped unharmed.

Around 27 people were killed in Israeli strikes across Gaza Thursday, day 45 of the bloody conflict. Others died of wounds, raising the overall death toll to 2,083 Palestinians since July 8.

The UN has identified about 70 percent of them as civilians.

On the Israeli side, 67 people have been killed, 64 of them soldiers.

One civilian was severely wounded when a mortar round hit an area not far from the Gaza border on Thursday, the army said.

In the 48 hours since the truce broke down, Gaza militants have launched 283 rockets, 219 of which struck Israel and another 44 which were shot down, the army said.

Israel's Football Association postponed the start of the new premier league season scheduled this weekend over fears of rocket attacks.

UN aid workers stepped up calls for an urgent ceasefire, warning that spiralling violence endangered their ability to respond to the needs of Gaza's 1.8 million people.

Despite the collapse of the negotiations, Palestinian president Mahmud Abbas held talks in Qatar with exiled Hamas chief Khaled Meshaal, official Palestinian and Gulf news agencies said.

The talks in Doha, where Meshaal is based, were hosted by Qatari emir Sheikh Tamim bin Hamad al-Thani, a key backer of Hamas.

Also present were Azzam al-Ahmed, who led the Palestinian delegation at truce talks in Cairo, senior negotiator Saeb Erakat and Palestinian intelligence chief Majid Faraj.

- Gaza arms embargo? -

Late Wednesday, Hamas's armed wing said there would be no further negotiations with Israel, and warned foreign airlines "to stop flying into Ben Gurion airport from 6 am (0300 GMT)".

Egypt's Air Sinai said it was cancelling its Thursday and Friday flights "due to the deteriorating security situation".

Otherwise, air traffic was functioning normally, except for a brief interruption "for security reasons", Israel Airports Authority (IAA) spokesman Ofer Lefler told AFP.

Last month, major US and European airlines suspended flights for two days after a rocket hit very close to a runway at Ben Gurion in a move hailed by Hamas as a "great victory".

Israeli confidence in Prime Minister Benjamin Netanyahu has steadily declined during the war, but his 53 percent approval rating is still higher than before the conflict, according to a survey for the private Channel 2 television.

British aid charity Oxfam, meanwhile, urged the international community to "immediately suspend transfers of arms or ammunition while there is serious risk that they could be used to violate international humanitarian law".

It said the widespread killing of civilians and destruction of civilian infrastructure during the Israeli operation was the worst it had witnessed in 20 years of working in Gaza.