Palestinians carry the dead body of a boy at a hospital in the central Gaza Strip Image Credit: Reuters

Gaza: The death toll from Israeli airstrikes on the Gaza Strip rose to 32 in three days after Palestinian officials said on Thursday six members of the same family had been killed.

Triggered by the targeted killing of a top leader of Islamic Jihad in Gaza, the two sides have been exchanging fire since Tuesday.

The Israeli military has been targeting what it said were Islamic Jihad sites and rocket-launching squads in Gaza.

"Six members of the Abu Malhous family, including three children and two women, were killed in an Israeli strike on their family home in Deir al-Balah in the southern Gaza Strip," the Palestinian ministry of health said.

The previous day, Israel said it targeted two Islamic Jihad leaders preparing to fire anti-tank missiles.

Air raid sirens wailed and fireballs exploded as air defence missiles intercepted rockets, sending Israelis rushing to bomb shelters.

In Gaza, residents surveyed damage and mourned the dead outside a mortuary and at funerals.

UN envoy Nickolay Mladenov arrived in Cairo on Wednesday afternoon, airport officials said, following reports he was to hold talks aimed at halting the fighting.

The UN and Egypt have been instrumental in mediating previous ceasefires between Israel and Gaza-based militants.

But a source close to the discussions warned the risk of further escalation remained high.

Israel killed senior Islamic Jihad commander Baha Abu al-Ata and his wife Asma in a targeted strike early Tuesday, prompting barrages of tit-for-tat rocket fire and air strikes.

The flare-up raised fears of a new all-out conflict between Israel and Palestinian militants in Gaza, who have fought three wars since 2008.

A total of 32 Palestinians had been killed by Thursday morning, including Ata and his wife as well as three children, according to Gaza's Hamas-run health ministry.

Schools in the blockaded Gaza Strip, of two million people, have been closed since Tuesday.

Israel's announced targets were confined to Islamic Jihad sites and not those belonging to Hamas.

"For the first time in the current era, Israel drew a distinction between Hamas and Islamic Jihad," commentator Ben Caspit wrote in Israeli newspaper Maariv.

Islamic Jihad is the second most-powerful fighting group in the Gaza Strip after Hamas and has taken responsibility for rocket fire

"As long as the Israeli warplanes bomb the Gaza Strip, the resistance will respond to the Israeli aggression and defend the Palestinian people," a joint statement from Gaza fighting groups said.

The flare-up comes at a politically sensitive time for Israel, with no new government in place after September elections ended in deadlock.