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

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 killed Eliahu Asheri, whose body was found buried near the West Bank city of Ramallah.

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

Sunday's capture of the Israeli soldier, Cpl. Gilad Shalit 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 Deputy Prime Minister Nasser Shaer, 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.

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."

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.