Gaza fighting raged on Wednesday, displacing thousands more Palestinians in the battered territory as U.S. Secretary of State John Kerry said efforts to secure a truce between Israel and Hamas had made some progress, according to Reuters.

U.S. aviation authorities lifted a ban on flights to Tel Aviv which had been in force for two days, prompted by rocket salvoes out of the Gaza Strip, but many other global airlines were avoiding the Jewish state.

Hamas leader Khaled Meshaal, speaking in Qatar, praised the group's fighters, whom he said had made gains against Israel and said he supported a humanitarian truce but a ceasefire would only be acceptable in exchange for easing Gazans' plight.

"Let's agree first on the demands and on implementing them and then we can agree on the zero hour for a ceasefire... We will not accept any proposal that does not lift the blockade... We do not desire war and we do not want it to continue but we will not be broken by it,” he said.

Adding to the pressure on Israel, UN High Commissioner for Human Rights Navi Pillay said there was "a strong possibility" that it was committing war crimes in Gaza, where 703 Palestinians, mostly civilians, have died in the fighting, according to Palestinian health officials.

Pillay also condemned indiscriminate Islamist rocket fire out of Gaza and the United Nations Human Rights Council said it would launch an international inquiry into alleged violations.

Israel denied any wrongdoing. "Get lost," Justice Minister Tzipi Livni said on her Facebook page in response to the investigation.

Kerry met Palestinian President Mahmoud Abbas, UN Secretary-General Ban Ki-moon and Israeli Prime Minister Benjamin Netanyahu on Wednesday. He later returned to Egypt, which shares a border with Gaza and has mediated with Islamist Hamas.

"We have certainly made some steps forward. There is still work to be done," said Kerry, on one of his most intensive regional visits since the peace negotiations he had brokered between Netanyahu and Abbas broke down in April.