GAZA CITY, OCCUPIED GAZA STRIP, AUG. 3 -- At least 300 people were rounded up and dozens held for questioning as Israeli troops blockaded the Gaza Strip today and extended a dragnet for suspects in the killing of a military police commander.

Soldiers erected a barbed wire fence around the commercial district of Gaza City where Capt. Ron Tal, 22, was shot in the head with a pistol at close range on Sunday. The Army said an area curfew would be extended at least until Tuesday.

The indefinite curfew confined about half of Gaza City's 150,000 Palestinians to their houses. Troops blocked roads leading to and from Gaza, keeping an estimated 60,000 Palestinians from jobs in Israel. The ports were also blockaded.

Israeli radio stations called the measures Israel's most sweeping acts of collective punishment in the occupied territories in years.

The 140-square-mile Gaza Strip, 40 miles south of Tel Aviv, is home to 600,000 Palestinian refugees and about 2,000 Jewish settlers. Two Israelis have been killed and four wounded in attacks there this year.

On Sunday night and Monday, Israeli soldiers mounted "wide searches everywhere in Gaza," an Army spokesman said.

After the shooting a man identifying himself as a member of Force 17, a unit of the Palestine Liberation Organization, called a news agency and claimed responsibility.

Defense Minister Yitzhak Rabin called Tal's death the work of Palestinian guerrillas.

Former Gaza mayor Rashad Shawwa said tensions had risen after some Israeli officials suggested that Palestinians in the occupied West Bank move to an Arab country.