JERUSALEM - Palestinian militants in the Gaza Strip bombarded southern Israel with dozens of mortars and rockets on Wednesday, sowing panic and despair there and burdening diplomatic efforts to revive a truce that expired over the weekend.

No Israelis were injured in the barrages. The attacks took a steeper toll in Gaza as explosives apparently misfired, wounding three civilians and killing two militants. One of the injured civilians works for a conflict resolution center.

Hamas, the Islamic militant group that rules Gaza, said the bombardment came in retaliation for the deaths of three of its fighters in a clash with Israeli troops late Tuesday. Israel said the militants were planting explosives in northern Gaza along the border fence.

About 60 rockets and mortars pelted southern Israel by midafternoon Wednesday, the military said. Rockets reached as far as Beit Hagdi, a small community about 20 kilometres from Gaza City, the military said.

Television footage showed gaping holes torn into buildings by projectiles.

"We heard the alarm and the whistling as it approached, and then we heard a big explosion," said Benny Gueta, whose windows were shattered in Ashkelon, 17 kilometres from the Gaza border.

"We can't live this way," Gueta told Israel Radio. "It's no way to live."

In Gaza, health officials said Iyad Dremly, a Palestinian attorney who works for the Palestinian Center for Conflict Resolution, was badly wounded in an explosion that ripped through his two-story apartment building in Gaza City.

Militants were firing rockets and mortars from the area, but the military said it did not carry out any attacks on Gaza, suggesting the blast was caused by misfired explosives.

Two other civilians were hurt when a rocket landed on another house several miles to the north in Beit Lahiya, the health officials reported. Before dawn, two militants were killed in southern Gaza when an explosive they were preparing went off, Hamas reported.

Before the violence escalated, Israel had agreed to open cargo crossings with Gaza on Wednesday to allow in a limited amount of food, medicines and fuel, including supplies from Egypt. But military spokesman Peter Lerner said the passages would remain closed in light of the militant barrages.

Israel has maintained a strict blockade of Gaza since the June 19 cease-fire began unraveling six weeks ago, allowing in only small quantities of essential goods. Egypt has also sealed its border crossing with the territory, which is Gaza's main gateway to the outside world.

The sanctions have deepened the destitution in Gaza, home to 1.4 million Palestinians who are confined to their tiny coastal strip. Gazans have worked around the blockade by bringing in goods through tunnels dug under the Gaza-Egypt border.