BAGHDAD, Iraq - Insurgents assassinated the highest-ranking Iraqi official in eight months today, gunning down the governor of Baghdad province and six of his bodyguards, and a suicide truck bomber killed 10 people at an Interior Ministry commando headquarters, the latest in a string of violence ahead of Jan. 30 elections.

Five American troops were slain in three separate attacks, officials said, in the deadliest day for the U.S. military in Iraq since a suicide bombing at a mess tent in Mosul on Dec. 21 killed 22 people, including 14 U.S. soldiers and three American contractors.

The militant group of Jordanian terrorist Abu Musab al-Zarqawi, Al-Qaida in Iraq, claimed responsibility for killing Gov. Ali al-Haidari and his bodyguards, according to a statement posted on a Web site known for carrying such claims.

"We tell every traitor and supporter of the Jews and Christians that this is your fate," the statement said. Its authenticity could not immediately be verified.

Iraq's insurgents repeatedly have targeted government officials and security forces, saying they are allies of the U.S.-led coalition.

More interim Iraqi government officials are saying the elections should be postponed to ensure a higher Sunni voter turnout, a sign the ongoing campaign of violence might be taking its toll on Iraqi resolve. The United States and Iraq's electoral commission, however, insist that voting take place as scheduled.

Sunni Arab clerics have called for a boycott and Iraq's largest Sunni political party announced it was pulling out of the race because of poor security that has seen insurgents kill scores of Iraqi security forces, as well as several election officials, in recent weeks.

Al-Haidari's three-vehicle convoy was passing through Baghdad's northern neighborhood of Hurriyah when unidentified gunmen opened fire, said the chief of his security detail, who asked to be identified only as Maj. Mazen.

"They came from different directions and opened fire at us," Mazen said, reached on al-Haidari's cell phone.

Al-Haidari was the target of another assassination attempt last year that killed two of his bodyguards. He is the highest-ranking Iraqi official killed since the former president of the now defunct Governing Council - Abdel-Zahraa Othman, better known as Izzadine Saleem - was assassinated in May.

Speaking in Thailand, Secretary of State Colin Powell said he was saddened by al-Haidari's death.

"It once again shows that there are these murderers and terrorists, former regime elements in Iraq, who don't want to see elections. They don't want the people of Iraq to chose new leaders. They want to go back to the past. They want to go back to the tyranny of Saddam Hussein's regime and that's not going to happen," Powell said.

Al-Haidari worked closely with the U.S.-led multinational forces on rebuilding the capital. In an interview published today in al-Mutamar newspaper, he said infrastructure in Baghdad was improving as a result of cooperation between his office and the troops.

He had not always sided with the Americans, however, demanding in October that the United States leave the Green Zone, the fortified home of the U.S. Embassy and the interim Iraqi government.

On Nov. 1, al-Haidari's deputy, Hatim Kamil, was shot to death on his way to work. The Ansar al-Sunnah Army militant group claimed responsibility for that attack.

In the American deaths, a roadside bomb killed three U.S. soldiers in Baghdad, and a soldier and a Marine were killed in other attacks outside the capital, the U.S. military said.

The three soldiers killed in the capital were with Task Force Baghdad, and two soldiers were wounded in the attack, which occurred about 11 a.m., the military said.

Elsewhere, a roadside bomb attack killed one 1st Infantry Division soldier and wounded another near Balad, 50 miles north of Baghdad.

A U.S. Marine assigned to the 1st Marine Expeditionary Force was killed in action in western Iraq's restive Anbar province, which includes the former insurgent stronghold of Fallujah.

Also today, a tanker truck packed with explosives detonated near an Interior Ministry commando headquarters in western Baghdad, killing 10 people and wounding about 60, the Interior Ministry said.

A suicide driver rammed the truck at a police checkpoint near the headquarters, which is also near an entrance of the Green Zone.

Eight Iraqi commandos and two civilians were killed, the Interior Ministry said.

Today's attacks came a day after violence that saw a roadside attack and three car bombs, one near the prime minister's party headquarters in Baghdad and others targeting Iraqi troops and a U.S. security company convoy. At least 16 people were killed Monday.

A car bomb near the Green Zone killed three Britons and an American working for U.S. security firms, their employers and Britain's Foreign Office said today.

The blast killed two British employees of U.S. security firm Kroll Inc., said Andrew Marshall, a London-based spokesman for the firm. A third Briton and an American employed by another U.S. firm, BearingPoint, also were killed, that company said.

The American was identified as Tracy Hushin, 34, who was working under contract for the United States Agency for International Development, coordinating training for Iraqis. The other victims were not immediately identified.

Later, a roadside bomb killed three Iraqi National Guardsmen and wounded two near Baqouba, 35 miles northeast of Baghdad, U.S. military spokesman Neal E. O'Brien said.

Defense Minister Hazem Shaalan, meanwhile, traveled to Egypt to seek help in getting Iraq's Sunni Muslim minority to take part in the elections. Leaders of the Sunni community, about 20 percent of Iraqis, say the country is far too unsafe to hold the vote.

A low turnout because of the fear of violence or a Sunni boycott could undermine the legitimacy of the country's first free elections since the overthrow of the monarchy in 1958.

Shaalan suggested that if Sunnis agreed to participate, the vote could be postponed by a few weeks to give them time to prepare. Iraq's Sunni areas, mostly surrounding and west of Baghdad, have seen some of the worst violence in recent weeks.

But Fareed Ayar, a spokesman for Iraq's Independent Electoral Commission, seemed adamant that no delay was envisioned. "The commission is still working on holding the elections on schedule," he said.