BAGHDAD, Iraq -- Insurgents attacked British troops at a checkpoint in central Iraq on Thursday, killing three and wounding eight in a suicide bomb and mortar barrage aimed at soldiers sent to the high-risk area to free U.S. forces for an assault on the militant stronghold Fallujah.

U.S. troops pounded Fallujah with airstrikes and artillery fire, softening up militants ahead of the expected assault. Loudspeakers at Fallujah mosques blared out Quranic verses and shouts of "Allahu akbar," or "God is great," during the assault, residents said.

The three British soldiers were from the Black Watch regiment, which was moved last month from relatively quiet southern Iraq to the dangerous area just south of Baghdad.

An Iraqi interpreter also was killed in the attack, British officials said. Britain's armed forces minister, Adam Ingram, said in London that the attack was carried out by a suicide bomber in a vehicle and that the British checkpoint also came under mortar fire.

The deaths bring the number of British troops killed in Iraq to 73. It was the worst single combat loss for the British since three Royal Military Police were killed in the southern city of Basra in August 2003.

A suicide car bomber also targeted a U.S. Marine convoy near Ramadi, 70 miles west of Baghdad, but only the attacker died in the explosion, U.S. officials said.

British Prime Minister Tony Blair agreed to a U.S. request to move British troops to central Iraq despite considerable opposition at home, even within his Labour Party.

Scottish Nationalist Party spokesman Angus Robertson warned that the deaths would have "profound implications" for public opinion in Scotland, where the Black Watch regiment is recruited.

U.S. and Iraqi officials want to clear insurgents from Fallujah and other Sunni Muslim areas north and west of Baghdad so elections can be held by the end of January. American officials plan to use a mixed American and Iraqi force to storm Fallujah, 40 miles west of Baghdad, if interim Prime Minister Ayad Allawi gives the go-ahead.

American aircraft were in action over Fallujah early Thursday, blasting militant positions in northeastern and southeastern parts of the city, the military said. U.S. batteries later fired two to three dozen heavy artillery shells at insurgent positions, the military said.

Militants and U.S. forces also clashed briefly in Ramadi, but no U.S. casualties were reported.

An Iraqi known for cooperating with Americans was killed near Ramadi, police said. The assailants stopped a car carrying Sheik Bezei Ftaykhan, ordered the driver to leave and pumped about 30 bullets into the sheik's body, police said.

The deteriorating security situation prompted the humanitarian organization Medecins Sans Frontieres, or Doctors Without Borders, to announce it was closing its operations in Iraq. CARE International withdrew from the country after its national director, Margaret Hassan, was kidnapped last month.

U.S. officials say contacts are still underway for a peaceful solution to the crisis in Fallujah, which worsened after Marines abandoned their three-week siege of the city last April, enabling Islamic militants to take control there.

In preparation for the planned offensive, Iraqi authorities have put together a team of Iraqi administrators to run the city after the fighting, Marine Maj. Jim West said Thursday.

West said $75 million has been earmarked to repair the city. The strategy is similar to one used when U.S. troops restored government authority in the Shiite holy city Nafaj last August after weeks of fighting with militiamen.

Elsewhere, an Iraqi National Guard patrol was attacked by a car bomb in Iskandariyah, 30 miles south of Baghdad, killing three people and wounding 15, Iraqi hospital officials said.

A suicide car bomber also killed three and wounded nine when his explosive-laden vehicle barreled into city government offices in Dujail, 50 miles north of the capital, police said.

As the wave of foreign kidnappings continued, Al-Jazeera television aired video of three Jordanian truck drivers seized by a militant group called Army of Islam. They were among seven truckers who came under attack Tuesday near Fallujah, the Jordanian Truckers Association said. One driver was killed, two others are missing and one reached Jordan.

More than 170 foreigners have been kidnapped and more than 30 of them have been killed in Iraq since Saddam Hussein's regime fell in April 2003.