Israeli forces have pounded multiple sites across the Gaza Strip, including the enclave's only power station, as diplomats intensified efforts to end the bloodshed.

Palestinian emergency services said that at least six people were killed and 20 injured early on Wednesday during prolonged bombardment of the southern town of Khan Younis.

Wednesday’s deaths bring the number of Palestinians killed during the 16-day Israeli assault on Gaza to 648, including scores of children. More than 4,000 people have been injured.

The number of Israelis who have died has climbed to 31 - 29 soldiers and two civilians. One other soldier remains missing, but is presumed dead, according to the Israeli army.

Gaza residents on Wednesday said Israel attacked the power station which provides electricity to half the population of Gaza.

A spokesman for the power station told Al Jazeera that its main equipment was hit last night, adding that now only 10 percent of Gazans received electricity.

Electricity supplies from Israel were cut short last week, after Israel said that rockets from Gaza had damaged the infrastructure.

A rocket fired from Gaza on Tuesday hit Tel Aviv’s Ben Gurion international airport prompted major US and European airlines to suspend their flights from and to Israel, a blow to Israel's economy.

Diplomatic efforts

But the US secretary of state, John Kerry, flew into Tel Aviv on Wednesday to try to broker a ceasefire.

He immediately set off for Jerusalem where he was to meet visiting UN chief Ban Ki Moon, after which he was to travel to the West Bank city of Ramallah for talks with Palestinian leader Mahmud Abbas, a State Department official said.

Kerry was in Cairo a day earlier, from where he called on Hamas to accept an Egyptian proposed-ceasefire.

Hamas has so far refused the Egyptian proposal, saying that any peace deal must include a pledge by Israel to open border crossings with Gaza and lifting the siege on the enclave.

The Palestinian faction is also demanding the release of dozens of prisoners who were freed in a 2011 swap for captured Israeli soldier Gilad Shalit but re-arrested this summer.