A massive explosion hit an American diplomatic convoy traveling in the Gaza Strip Wednesday. Reports indicate three Americans were killed and another seriously injured.

The blast occurred mid-morning local time, just south of the Erez crossing between Israel and the Gaza Strip. An apparent roadside bomb went off as a U.S. diplomatic convoy escorted by Palestinian police, passed by. U.S. officials confirm the casualties were "American Embassy casualties." Reports from the scene say the blast ripped apart a silver Cherokee Jeep carrying security personnel. Television footage showed a mangled vehicle and a crater in the road carved out by the explosion.

Israeli troops moved in to help evacuate the casualties.

Palestinian Prime Minister Ahmed Qureia strongly condemned the attack.

"We condemn it strongly; we send all condolences to the families of those who have been killed there, and we hope for those who are injured that they will recover very soon and we will investigate from our side this," he said.

No one has claimed responsibility for the attack so far. The bomb blast seems to have specifically targeted the American convoy, making it the first attack against American officials in the past three years of the intifada.

Palestinian officials said the convoy contained members of a U.S. monitoring team in Gaza who came on the invitation of the Palestinian Authority.

U.S. diplomats and CIA representatives routinely travel in Palestinian areas as part of a team to monitor and supervise the implementation of a U.S. backed international peace plan.

Israeli officials say the attack shows the indiscriminate nature of what they term Palestinian terrorism. They say it also shows the Palestinian Authority is still not doing anything to stop such terrorism.