Two car bombs wounded American and Iraqi troops west of the capital Sunday and a few hours later the U.S. military announced the arrest of a senior Iraqi National Guard (search) commander on suspicion of ties to insurgents, underscoring the challenges to building a strong Iraq security service capable of restoring stability.

The two attackers who died in the twin blasts tried to ram their cars into a National Guard base in Kharma, a town on the outskirts of the insurgent stronghold of Fallujah (search), a U.S. military official said on condition of anonymity.

The number of U.S. and Iraqi casualties was not immediately clear, but a statement from the U.S. Marines said there were no serious injuries among American troops at the base.

The National Guard is the centerpiece of U.S. plans to turn over security responsibilities after elections slated for January and guardsmen have been targeted repeatedly by insurgents who are trying to undermine Iraq's interim government and drive out the U.S.-led coalition.

But the threat may not only come from outside the force. Guard Brig. Gen. Talib al-Lahibi (search), who previously served as an infantry officer in Saddam Hussein's army, was detained Thursday in the province of Diyala, northeast of Baghdad, a U.S. military statement announced.

The statement provided no details, but said he was suspected of having links to militants who have been attacking coalition and Iraqi forces for 17 months. Al-Lahibi was the acting head of the Iraqi National Guard for Diyala province, said Maj. Neal O'Brien, spokesman for the U.S. Army's 1st Infantry Division.

Meanwhile, an Egyptian diplomat and two British Muslim leaders urged religious leaders here to help secure the release of hostages.

Egyptian official Farouq Mabrouk sought help for six Egyptian telecommunications workers abducted with four Iraqis last week. Mabrouk refused to speak to reporters after his 30-minute meeting with Harith al-Dhari, who heads the Association of Muslim Scholars, a conservative organization that has helped win the release of other foreign captives.

Gunmen abducted two of the Egyptians on Thursday in a raid on their firm's Baghdad office -- the latest in a string of kidnappings targeting engineers working on rebuilding Iraq. Eight other employees, four Egyptians and four Iraqis, were seized outside of Baghdad on Wednesday.

Two senior officials of the Muslim Council of Britain were in Baghdad seeking freedom for hostage Kenneth Bigley, a British civil engineer kidnapped Sept. 16 with two Americans who were later beheaded.

After meeting with Muslim and Christian leaders, Daud Abdullah and Musharraf Hussain told reporters, "We cannot hold a British citizen responsible for what [British Prime Minister] Tony Blair did."

A posting on an Islamic Internet site Saturday claimed followers of Jordanian terror mastermind Abu-Musab al-Zarqawi had killed Bigley, but the British Foreign Office said the claim was not credible.

Bigley's brother, Paul, said Sunday he was told the captive was still alive.

"I have received information this evening that Ken is alive," Paul Bigley said by video link to a gathering at the Brighton, England, conference of Blair's Labour Party.

He provided few details, but he urged Blair to make a personal plea for his brother's release.

"All I am asking is for communication," Paul Bigley said. "Just simply send a bloody fax pleading for my brother's life."

Earlier Sunday, Blair said his government was doing everything it "properly and legitimately" could to secure Ken Bigley's release. The prime minister's office said Blair phoned the Bigley family again Sunday, as he did earlier in the week.

Yasser el-Sirri, head of the London-based Islamic Observation Center, told The Associated Press his organization appealed Thursday to al-Zarqawi's Tawhid and Jihad group to free Kenneth Bigley after the British government rejected its demands to free Muslim women from jail.

"We have received a positive answer that the group will consider our appeal when they decide his fate, and they confirmed that he is alive," said el-Sirri, whose organization often is a reliable source of information on Muslim militants.

Pressed on how he received the information on Kenneth Bigley, el-Sirri would only say it was "through a mediator in Iraq."

More than 140 foreigners have been kidnapped in Iraq -- some by anti-U.S. insurgents and others by criminals seeking ransom. At least 26 have been killed, including the two American civil engineers, Eugene Armstrong and Jack Hensley.

Persistent violence, coupled with the coalition forces' lack of control in key parts of the country, have raised questions about the feasibility of holding elections by the Jan. 31 deadline.

Secretary of State Colin Powell said Sunday that the United States is committed to allowing all Iraqis the chance to vote, but the top U.S. military commander in the region cautioned against expecting that sort of achievement.

Both Powell and Gen. John Abizaid spoke of a major political and military effort before the scheduled elections to take back areas that insurgents now control.

Powell said planning is under way for an Iraqi conference, possibly next month, that would include the leading industrialized nations and regional powers, including Iran and Syria.

"This was a way to reach out to Iraq's immediate neighbors and persuade them that this is the time to help Iraq, so that the region can become stable," Powell said in a televised interview.

In other violence Sunday, U.S. troops and insurgents traded fire in Ramadi, west of Baghdad, resulting in at least three people being killed and four wounded, witnesses and hospital officials said. Insurgents fired mortar rounds and rockets at two U.S. positions west and east of the city, and U.S. forces responded with shelling, striking a house in Tamim neighborhood, witnesses said.

A rocket slammed into a busy Baghdad neighborhood, killing at least one person and wounding eight, hospital officials and witnesses said.

Hours after the attack, another loud blast shook the area near the Green Zone, site of the U.S. Embassy and interim Iraqi government offices. Smoke rose above the zone and alert sirens sounded. It was not clear if anything had been hit.

Five members of the U.S. House of Representatives were in the embassy at the time, but none was injured.

The delegation included Rep. Stephanie Herseth of South Dakota, Rep. Mark Udall of Colorado, Rep. Tom Osborne of Nebraska, Rep. Ernest Istook of Oklahoma and Rep. Scott Garrett of New Jersey. The group was to return to the United States on Tuesday, Herseth said.