GAZA/JERUSALEM, May 13 (Reuters) - Palestinian militants in Gaza resumed rocket fire on Israel early on Saturday after Israeli aircraft bombed Islamic Jihad targets in the enclave overnight, as fighting entered a fifth day.

Egypt has been trying to mediate a truce to the flare-up, which has so far left at least 33 Palestinians and one Israeli dead.

The violence extends more than a year of resurgent Israeli-Palestinian violence that has killed more than 140 Palestinians and at least 19 Israelis and foreigners since January.

The military said it struck Islamic Jihad command centres and rocket launchers in its pre-dawn operations. Grainy black and white aerial footage it released showed explosions and clouds of smoke rising from bombed sites.

A few hours later Gaza militants fired rockets, setting off sirens and sending Israelis in border communities running to bomb shelters. There were no reports of casualties.

Six top Islamic Jihad commanders have been killed since Tuesday, when Israeli forces launched a campaign against the group, saying it was planning attacks.

Islamic Jihad, the largest armed group in Gaza after the ruling Islamist Hamas, has since fired almost 1,000 rockets, some deep into Israel. One woman was killed on Thursday when an apartment was struck by a rocket in a Tel Aviv suburb.

At least four women and six children have died in densely populated Gaza, an impoverished coastal territory blockaded by Israel and Egypt since 2007. Israel says four Palestinians were killed by misfired Gaza rockets, which Islamic Jihad has denied.

Islamic Jihad spurns coexistence with Israel and preaches its destruction. Top ministers of Israel's religious nationalist government rule out any state sought by Palestinians in territories captured by Israel in the 1967 Middle East war.