U.S. warplanes, tanks and artillery units struck the insurgent stronghold of Fallujah (search) on Saturday, killing at least eight people and wounding 15 in a day that saw new violence across the country. The U.S. military announced the deaths of four Marines and a soldier.

The American soldier was killed when a homemade bomb exploded Saturday. The Marines were killed in three separate incidents Friday while conducting security operation in Anbar province (search), which includes Fallujah, Ramadi, and other places where U.S. and insurgent forces regularly clash.

In Baghdad, gunmen opened fire on a vehicle carrying Iraqi National Guard (search) applicants, killing six people, police said. The slayings were part of a militant campaign targeting Iraqi security forces and recruits in a bid to thwart U.S.-backed efforts to build an Iraqi force capable of taking over security from American troops.

Police Lt. Omar Ahmed said the group had just left a national guard recruiting center where they had signed up to join the force in the west Baghdad neighborhood of Al-Jamiyah when the attack occurred.

Underscoring just how dependent the government still is on outside help, interim Prime Minister Ayad Allawi urged the international community to set aside its differences over the legality of the invasion to oust Saddam Hussein and "stand fast by Iraq."

"We need to broaden the base of troop-contributing countries to (the multinational force) so that we would stand more determined and be better equipped to confront terrorism," he told the U.N. General Assembly in New York on Friday.

The U.S. military said the Fallujah strikes targeted a meeting point in the center of the city for fighters loyal to Jordanian-born terror mastermind Abu Musab al-Zarqawi.

"Intelligence sources reported that Zarqawi terrorists were using the site to plan additional attacks against Iraqi citizens and multinational forces," the military said in a statement.

American forces also bombed rebel-built fortifications late Friday, including concrete and earthen barriers and roadblocks, used to restrict movement in the city and mount attacks on Marine positions outside Fallujah, the military said in a separate statement Saturday.

Dr. Dhiya al-Jumaili of Fallujah General Hospital said at least eight people were killed and 15 wounded, including women and children.

Explosions lit up the night sky for hours and at least two buildings in the city center were wrecked, witnesses said. The Fallujah mosque switched on its loudspeakers and clerics chanted prayers to rally the city's residents.

Earlier Friday, Marines fired artillery rounds after observing a number of insurgents getting out of a vehicle with a mounted machine gun, said 1st Lt. Lyle Gilbert, a Marine spokesman.

American troops have not entered Fallujah since ending a three-week siege of the city in April that left hundreds dead.

Saturday's strikes were the latest in a string of attacks against al-Zarqawi's network, which has claimed responsibility for numerous car bombings, kidnappings and other assaults meant to destabilize Iraq's U.S.-backed interim authorities and drive coalition forces from the country.

Among the hostages Zarqawi's Tawhid and Jihad group claims to have taken is Briton Kenneth Bigley, kidnapped with two Americans on Sept. 16. The Americans were beheaded, one purportedly by Zarqawi himself.

On Friday, the Muslim Council of Britain sent a pair of negotiators to meet with religious leaders in Baghdad to try to win Bigley's release. The group described Daud Abdullah and Musharraf Hussain as "well-respected figures in the British Muslim community."

A Web posting on Saturday claimed that Bigley had been killed. The claim could not immediately be verified, and the Foreign Office in London described the site as "discredited."

"It's just a posting," a Foreign Office spokeswoman said on condition of anonymity. "We can't see there's anything credible in this at all."

The site also claimed that seven British troops had been captured, but Capt. Donald Francis, a spokesman for the British military said that all forces "are accounted for."

He had no information on the claim to have killed Bigley.

Iqbal Sacranie, the group's secretary-general, on Friday urged Bigley's captors to free him.

"Our religion Islam does not allow us to harm the innocent," said Iqbal Sacranie, the group's secretary-general. He urged the kidnappers to "release this man back into the arms of his waiting family."

Also Friday, authorities said kidnappers had seized six Egyptians and four Iraqis working for the country's mobile phone company. Gunmen abducted two of the Egyptians on Thursday in a bold raid on the firm's Baghdad office — the latest in a string of kidnappings targeting engineers working on Iraq's infrastructure, in a bid to undermine the U.S.-allied interim government. Eight other company employees were seized outside Baghdad on Wednesday.

More than 140 foreigners have been kidnapped in Iraq — some by anti-U.S. insurgents and some by criminals seeking ransoms. At least 26 of them have been killed.