GAZA CITY (AFP) - Palestinian fighters bombarded southern Israel on Thursday after a Hamas commander’s house in northern Gaza was blown up in a blast which killed seven people, including a four-month-old baby.

The attacks started immediately after the explosion which Palestinian medics said also wounded 51 people, among them women and children, in and around the two-storey building.

The Israeli military said nearly 50 rockets and mortar rounds were fired from the Gaza Strip following the explosion, which Hamas blamed on the Jewish state despite its denial of involvement.

“Only yesterday, Israel decided to give a chance to the Egyptian initiative which could have brought calm to the south,” the Israeli prime minister’s spokesman Mark Regev told AFP.

“The barrage of rockets today shows that Hamas has no interest in calm and is committed to violence, terror and murder.” However at Wednesday’s meeting, the Israeli Security Cabinet also ordered the military to make the necessary preparations for a major ground offensive against Gaza if the Egyptian-brokered truce talks fail to bear fruit, prompting Hamas to ridicule the genuiness of its stated desire for a ceasefire.

Witnesses and Hamas said Thursday’s blast that levelled a house in Beit Lahiya was caused by an Israeli air strike, but the army denied any involvement, saying it could have been an accidental explosion.

The blast caused widespread devastation.

“The IDF [Israel army] has no connection whatsoever to the events the Palestinians are describing. Our air force and land forces did not operate at that time,” spokeswoman Major Avital Leibowitz told AFP.

Hamas’ Al Aqsa television channel said the house belonged to a local commander of the armed wing of the Islamist movement, and added that he was not at home at the time.

Many of the victims belonged to one family, said Muawiya Hassanein who heads the Gaza emergency services.

“We blame this crime on the Israeli occupation,” Hamas spokesman Taher Nunu said in Gaza City. “We are used to Israel not admitting to its crimes.” Another Hamas official, Mushir Al Masri, told Al Aqsa: “The enemy must pay the price. We will not remain passive after this horrible crime.” Two Gaza fighters were killed by Israeli forces earlier on Thursday in operations before the house blast and a clash after the explosion, Palestinian emergency services said.

One fighter who fired at Israel was killed in an air strike near Khan Younis and another died in a firefight with Israeli troops in the Beit Lahiya area, they said.

The Israeli military confirmed the air strike and said soldiers fired on a group of Palestinians who approached the fence separating Israel from Gaza, hitting one.

At least 501 people, nearly all Palestinians and the majority of them Gaza fighters, have been killed since peace talks between Israel and the Palestinian leadership resumed last November, according to an AFP count.

That tally does not include the dead in Thursday’s house blast.

There have been several cases in the past when fighters accidentally set off deadly blasts while assembling makeshift explosive devices.

Egypt mediation

Israel joined a new round of Egyptian-brokered negotiations on a proposed truce in and around Gaza on Thursday after deciding to give the talks one last go while preparing for military action if they fail.

Amos Gilad, a top aide of Defence Minister Ehud Barak, arrived in Cairo for a meeting with Egyptian intelligence chief Omar Suleiman, who has been mediating between Israel and Palestinian resistance groups, officials said.

“Egyptian officials will hear from Mr Gilad the Israeli position on bringing about the period of calm,” an Egyptian source told the official MENA news agency.

The official “expressed hope that the truce between Israel and the Palestinins would come soon in order to lift the blockade imposed on the Palestinian people”, MENA said.

In Israel, Barak told reporters his country “must assess the possibilites of reaching a calm” but that “our duty is to ensure security around the Gaza Strip and we shall do so.

“Our military is strong and we are ready. As soon as the order is given, we will act,” he added, stressing that Israel must first “try to reach the same results without turning to the armed forces”. Hamas, the Islamist movement that seized power in Gaza last June, has ridiculed Israel for claiming it wants a truce while at the same time gearing up for a military offensive.

The Maariv daily said that following a meeting on Wednesday, Israel’s Security Cabinet gave truce efforts another two weeks.

If Palestinian fighters do not stop firing rockets and mortars at southern Israel within that timeframe, the military will be given the green light to launch a ground operation deep inside the Gaza Strip, the paper said.

But if fighters do hold their fire, Israel will then ease the blockade it imposed after the June 15, 2007 Hamas takeover, when the Islamists ousted forces loyal to secular Palestinian President Mahmoud Abbas.

Israel would then allow more humanitarian equipment and supply trucks to enter Gaza, army radio said.

The authorities would also allow the reopening of the Rafah crossing with Egypt, Gaza’s only one that bypasses Israel, but only if a captured Israeli soldier is released, the radio said.

Officials made Israel’s agreement to a truce conditional on progress in efforts to free Corporal Gilad Shalit, 21, who was seized by fighters from Hamas and other groups in a cross-border raid two years ago.