Three people were killed and one injured when an American convoy was hit by a massive blast in the Gaza Strip near the border with Israel on Wednesday, reports said.

The CNN quoted US sources as saying that the dead and injured were taken to Israel.

The BBC quoted sources as saying that the dead were American security guards.

Israel Radio put the toll at four.

It was not clear if the explosion, near Beit Hanoun, was the result of a suicide bombing or a roadside bomb.

US Ambassador John Wolf was not in the country at the time of the attack, the embassy said. Media reports had said he was in the convoy.

The new Palestinian Prime Minister, Ahmed Qurei, condemned the attack. "We are sorry about it. We condemn it strongly. We will investigate it."

It was the first time a US target had been hit inside the Palestinian territories.

The blast came just hours after the US vetoed a United Nations Security Council resolution condemning Israel's controversial West Bank barrier.