Israeli troops rounded up dozens of ministers and lawmakers from the Palestinians' ruling Hamas party on Thursday, while forging ahead with a military campaign in Gaza meant to win the release of an Israeli soldier held by Hamas gunmen.

Israeli warplanes also buzzed the summer home of Syria's president, Bashar Assad, who harbors the hard-line Hamas leaders who Israel says ordered the kidnapping.

CountryWatch: Israel

Adding to the tension, the body of a kidnapped 18-year-old Jewish settler who was shot in the head was found in the West Bank, Israeli security officials said. Palestinian militants said they executed Eliahu Asheri, whose body was found buried near the West Bank city of Ramallah.

The soldier's capture on Sunday by Hamas' military wing and two affiliated groups, and Israel's subsequent military incursion into Gaza threatened to bring the two sides to the brink of all-out war. Hamas, which took over the Palestinian Authority after winning parliamentary elections in January, has resisted international pressure to renounce violence and recognize Israel.

An Israeli military official said a total of 64 Hamas officials were arrested in the early morning roundup. Of those, Palestinian officials said seven are ministers in Hamas' 23-member Cabinet and 20 others are lawmakers in the 72-seat parliament.

Palestinian parliament speaker Abdel Aziz Duaik and Religious Affairs Minister Nayef Rajoub, brother of former West Bank strongman Jibril Rajoub of the rival Fatah party, were among those rounded up. There were conflicting reports about whether Deputy Prime Minister Nasser Shaer, who has called for the release of Israeli Cpl. Gilad Shalit, was arrested.

Officials will be questioned and eventually indicted, the Israeli army and government officials said.

Israeli Foreign Ministry spokesman Mark Regev said the ministers and lawmakers were not taken as bargaining chips for Shalit's release, but because Israel holds Hamas responsible for attacks against it.

"The arrests of these Hamas officials ... is part of a campaign against a terrorist organization that has escalated its war of terror against Israeli civilians," Regev said.

Israel has said it would not negotiate Shalit's release with the militants and has rejected demands to free Palestinian prisoners in exchange for information about the captured soldier.

Palestinians were outraged by the arrests.

"We have no government, we have nothing. They have all been taken," said Saeb Erekat, an ally of the moderate Palestinian president, Mahmoud Abbas. "This is absolutely unacceptable and we demand their release immediately."

Although the Israeli action was touched off by the soldier's capture, Israeli Prime Minister Ehud Olmert's government has also been alarmed by a surge in the firing of homemade rockets on Israeli communities bordering Gaza.

A militant offshoot of Abbas' Fatah party said it had fired a homemade rocket with a chemical warhead at the southern Israeli town of Sderot late Wednesday, the first such claim. The Israeli military said it did not detect a rocket fired then, and there was no way to verify the claim.

Israeli warplanes, tanks and thousands of troops began moving into Gaza overnight Tuesday. They knocked out Gaza's only power station, made main roads impassable and took over Gaza's long-closed airport. Aircraft bombed empty Hamas training camps, witnesses said, and flew low over the coastal strip in an apparent attempt to intimidate.

Airstrikes against the training camps continued on Thursday, with two strikes against camps in southern Gaza used by Hamas and the Al Aqsa Martyrs' Brigades, a Fatah offshoot.

No deaths or injuries have been reported in any of the attacks.

But the disabling of Gaza's electric power plant raised the specter of a humanitarian crisis. The Hamas-led government warned of "epidemics and health disasters" because of damaged water pipes to central Gaza and the lack of power to pump water.

The incursion has focused so far on southern Gaza, where the military thinks Shalit is being held. But the military signaled the prospect of a new front being opened in the northern part of the strip when it dropped leaflets late Wednesday into the area, urging residents to avoid moving in the area because of impending military activity. Security officials said it could take days before a second front was opened.

Israeli army bulldozers moved in Thursday to clear agricultural lands in northern Gaza, witnesses said, apparently so Palestinians couldn't hide there. A small number of tanks entered a buffer zone between southern Israel and Gaza, as they have done in recent weeks.

Olmert has threatened harsher action to free the soldier, though he said there was no plan to reoccupy Gaza. Abbas deplored the incursion as a "crime against humanity."

Abbas and Egyptian dignitaries tried to persuade Syria's Assad to use his influence with Hamas' Damascus-based political chief, Khaled Mashaal, to free the soldier. Assad agreed, but without results, said a senior Abbas aide.

In a clear warning to the Syrian president, Israeli airplanes flew over his seaside home near the Mediterranean port city of Latakia in northwestern Syria, military officials confirmed, citing the "direct link" between his government and Hamas. Israeli television reports said four planes were involved in the low-altitude flight, and that Assad was there at the time.

Syria confirmed Israeli warplanes entered its airspace, but said its air defenses forced the Israeli aircraft to flee.

Israeli Justice Minister Haim Ramon said Wednesday that the hard-line Mashaal, who appears to be increasingly at odds with more moderate Hamas politicians in Gaza, is an Israeli assassination target. Israel tried to kill Mashaal in a botched assassination attempt in Jordan in 1997.

The Popular Resistance Committees in Gaza, which has strong links to Hamas, said it executed Asheri, kidnapped in the West Bank. An Israeli military official said he was shot in the head shortly after he was abducted Sunday. The PRC had said it would execute the hostage if Israel did not halt its invasion of Gaza.

Government spokesman Asaf Shariv said Asheri's killers would be arrested, and Israel would try to bring them to trial.

"Their days as free people are numbered," Shariv said.

Militants also say they kidnapped another Israeli, a 62-year-old man from the central Israeli city of Rishon Lezion. But police said Thursday they found the man's body in his hometown in Israel, and that he apparently died of medical problems.