Palestinian police detained three suspected militants and hunted for two more over a bomb attack on a U.S. diplomatic convoy that killed three security guards in the Gaza Strip, Palestinian security sources said yesterday.

The announcement of the arrests followed world pressure on Palestinian authorities to crack down on militants after the bombing, the first to kill Americans during a three-year-old uprising against Israel for statehood.

Security sources said the three men belonged to the Popular Resistance Committees, an umbrella group of militants that has taken responsibility for previous roadside bombings against Israeli forces. The group denied any role in the convoy attack.

The three were detained in the Jabalya refugee camp, a militant hotbed next to the site of the attack. Two more members of the group were being sought, the sources said.

?Yesterday, a few hours after the bombing...Palestinian security forces detained three people as part of the investigation conducted by the Palestinian Authority into the incident,? a security official told Reuters in Gaza.

A leader of the Popular Resistance Committees confirmed the arrested men were members, but said: ?We made clear to the Palestinian Authority we had nothing to do with the bombing. We were stunned by the unjustified arrests.?

Many members of the Popular Resistance Committees are former members of the Islamic militant group Hamas or Palestinian President Yasser Arafat?s Fatah movement.

The United States, the United Nations and European Union blamed lax Palestinian security for the bombing and demanded reforms by Palestinian authorities to rein in militant violence, a central requirement of an internationally backed peace plan.

Arafat cites concrete action

Arafat said he had taken ?concrete? action, alluding to the arrests. ?We sent our security groups (to investigate) and from yesterday we did not sleep...There is something concrete which we have done,? he told reporters at his West Bank compound.

?I?m saying (we have done) something ? (although) not all we are looking for,? he said, speaking in English. ?We are condemning it (the attack) completely. It is very serious, dangerous and not only against the Americans but against the Palestinians before it is against the Americans.?

The United States sent a Federal Bureau of Investigation (FBI) team to the region and made clear Washington would play a key role in inquiries.

Israeli Defence Minister Shaul Mofaz told reporters his government would do all it could to find the attackers. ?We are treating (this) like an attack on the Israeli army, and will do everything we can to get our hands on the perpetrators.?

U.S. Secretary of State Colin Powell said the bombing would not deter Washington from its ?road map? peace plan, which envisages a Palestinian state in territory Israel occupied in the 1967 Middle East war.

U.S. President George W. Bush said Palestinian authorities should have acted long ago ?to fight terror in all its forms?.

?The failure to create effective Palestinian security forces dedicated to fighting terror continues to cost lives,? he added.

The Americans died when a bomb apparently detonated by remote control crumpled their armour-plated jeep, tore a crater in the road and flung body parts about.

In Gaza?s Rafah refugee camp, Palestinian witnesses said a Palestinian policeman was killed in a gun battle with Israeli forces who swept in overnight. Another six people were wounded, including four under 18, hospital sources said.

The army said the raid was part of an operation against arms-smuggling tunnels near the border with Egypt.

Nidal al-Mughrabi