GAZA CITY, Gaza Strip – Israeli warplanes killed six people in an attack early Wednesday on a Gaza City meeting of Hamas commanders, Israelis and Palestinians said, while Israel’s military expanded an offensive in the region with an incursion in the southern Gaza Strip.

The military said it attacked the Gaza City residence because it was a “meeting place for terrorists.” It also confirmed Israeli forces were operating in southern Gaza as part of an effort to win the release of a captured soldier.

With tanks and troops on the move in the south, a huge explosion destroyed the house of Hamas activist Dr. Nabil al-Salmiah. Health Minister Bassem Naim said at least six people were killed including two children, and 27 wounded.

As rescue workers dug through the rubble hours later, it was still not clear if top-level Hamas figures were hit in the airstrike. Nervous Hamas officials carefully inspected the bodies, saying a senior Hamas commander was among the wounded but they did not know who was killed.

Abu Obeideh, spokesman for the military wing of Hamas, issued an unusually strong condemnation, using language employed only when Israel has assassinated top Hamas leaders. “We will make the leaders of the Zionist regime regret this Nazi crime,” said part of his long statement.

Witnesses said the house was struck by a missile fired from an Israeli warplane. The Israeli military said it attacked the house because it was a “meeting place for terrorists” who were planning attacks and rocket launching.

Palestinian rescue teams dodged broken water pipes and electricity wires to get to injured people screaming for help. The scene resembled the aftermath of a 2002 attack, when an Israeli warplane dropped on one-ton bomb on the house of a Hamas leader in Gaza, killing him and 14 other people, including nine children.

A neighbor, Safwan Amamour, 39, said he and his wife were cleaning their house next door when they heard a huge explosion, and he was hit by flying rubble.

As doctors stitched a cut next to his eye, he recounted grisly scenes of dismembered bodies. “No words can describe this destruction, this hellish damage, which I will remember of the rest of my life,” he said.

Hamas official Ismail Radwan pledged to hit back at Israel. “It was a terrible, bloody massacre, and the Zionists will pay a heavy price for it,” he said.

The expansion of the Gaza offensive came hours after Israeli leaders ordered incursions into areas of the territory they have not yet entered.

Palestinians said they saw Israeli bulldozers leveling farmland and tanks moving across the border near the southern Gaza city of Khan Younis. The military ordered Palestinian security to leave their forward positions in the area.

The Israelis have not entered Khan Younis during the current offensive. Before Tuesday, Israeli forces had entered southern and northern Gaza and have approached Gaza City.

Israel launched its offensive on June 28, three days after Palestinian militants linked to the Hamas-led government captured an Israeli soldier in a cross-border raid. The operation was expanded last week to halt Palestinian militants from firing homemade rockets into Israel.

Prime Minister Ehud Olmert and his defense minister, Amir Peretz, ordered the new incursions into Gaza after Hamas leader Khaled Mashaal said Monday he would not free the captive soldier, 19-year-old Cpl. Gilad Shalit, security officials said on condition of anonymity because of the sensitivity of the operation.

Mashaal called Shalit a prisoner of war and demanded a prisoner swap _ which Olmert has ruled out.

Responding to Mashaal’s statement, Shalit’s father, Noam, called on Hamas to allow the Red Cross to visit his son. Under Geneva Conventions, the Red Cross is supposed to have access to prisoners of war.

Israel has demanded the unconditional release of its soldier to end the offensive.

The invasion _ Israel’s largest ground operation in Gaza since withdrawing from the area last year _ has caused widespread destruction, knocked out much of Gaza’s power supply and left more than 50 Palestinians dead, most of them gunmen. One Israeli soldier has died.

The European Union began delivering aid to Gaza in a bid to repair some of the damage. Moderate Palestinian President Mahmoud Abbas said he had received $50 million from the Arab League.

It was the first aid delivered under internationally backed funding restrictions that bypass the Palestinian government led by the militant group Hamas since March.

Officials said the money had bypassed Hamas because of the international boycott. The European Union, along with Israel and the U.S., considers Hamas a terrorist group.

Mohammed Awad, the Palestinian Cabinet secretary, said Hamas agreed to allow Abbas to handle the money. He said the funds would be used to pay civil servants, who have not received salaries in four months.

The European Commission said it has started delivering $765,000 in monthly aid to hospitals in the Gaza Strip.

EU spokeswoman Emma Udwin said the funds _ to purchase fuel for emergency generators at Gaza hospitals _ was requested by Abbas after Israel destroyed six transformers at a power plant during its Gaza offensive. Gaza now has only sporadic electricity, almost all of it provided by Israel.

In Gaza, Hamas Prime Minister Ismail Haniyeh said the area is “on the verge of a genuine humanitarian crisis.”

“There are shortages of food, fuel and essential needs of Palestinian citizens,” he told his Cabinet, calling on the United Nations, Arab League, Muslim countries and the rest of the international community to help.

Also on Tuesday, a 15-month-old Palestinian boy injured in an Israeli missile strike last month died of his wounds at an Israeli hospital.