Palestinian police have arrested several militants suspected of involvement in Wednesday's bomb attack on an American diplomatic convoy in the Gaza Strip. The blast killed three American security guards, and has brought renewed pressure on the Palestinian Authority to crack down on militants.

Palestinian police moved into the Jebalya refugee camp in Gaza early Thursday, and arrested several militants belonging to the Popular Resistance Committees, a splinter group made up largely of former security officials and breakaway members of the mainstream Palestinian Fatah movement.

The Palestinian Authority is under growing pressure to find and arrest those responsible for Wednesday's attack on the American convoy.

U.S. security personnel and diplomats were on their way to Gaza City to meet with Palestinian academics about Fulbright scholarships. The three Americans were killed when a powerful bomb detonated as their car passed, destroying the armored vehicle and leaving behind blood, body parts and mangled metal.

The main Palestinian militant groups, including Hamas, Islamic Jihad and the al-Aqsa Brigades were quick to deny any involvement in the attack.

Palestinian Authority President Yasser Arafat and his Prime Minister Ahmed Qureia strongly condemned the attack, and promised to investigate. President Bush said the Palestinian Authority should have cracked down on terrorists long ago. European Union foreign policy chief Javier Solana is reported to have told Mr. Arafat that condemnation and excuses are not enough, but that tough action is needed.

A team of American experts with the Federal Bureau of Investigation is expected to assist in the investigation of the attack, working closely with Israeli police.

Violence continued on the ground Thursday, as Israeli security forces, backed by dozens of armored vehicles carried out another raid into parts of the Rafah refugee camp in the southern Gaza Strip. The military says it is conducting the operations to shut down tunnels being used by Palestinian militants to smuggle in weapons from neighboring Egypt.

A Palestinian security official was reported killed and more than a dozen people were injured in sporadic gun fights during Thursday's overnight operation.