In one of the highest profile abductions yet, kidnappers Tuesday seized Margaret Hassan, the head of CARE International in Iraq and one of the best-known aid workers in the region.

Hassan, who was born in Britain but has lived in Iraq for 30 years, was taken from her home in the Khadra neighborhood of western Baghdad, CARE officials confirmed. Al Jazeera television later aired footage of Hassan sitting in a room and looking anxious, wire services reported.

Also Tuesday, a mortar attack on an Iraqi National Guard base killed four guardsmen and wounded up to 80, the U.S. military said in a statement.

The attack at about 9:45 a.m. occurred near the town of Taji, north of Baghdad. U.S. helicopters were used to evacuate the injured, the statement said. It was one of numerous similar attacks that have killed scores of Iraqi police and guardsmen over the past year.

An American civilian working for KBR, a subsidiary of the U.S. firm Halliburton, was also killed in a separate early morning attack on a U.S. base in Baghdad, Halliburton spokeswoman Megan Mason told the Associated Press. A U.S. soldier was also wounded in the mortar and rocket attack. No identities were released.

Hassan's kidnapping comes at a time when British Prime Minister Tony Blair is planning to dispatch hundreds of British troops to an area just south of Baghdad to supplement U.S. forces. Britain has 7,500 troops in Iraq. While there was no known evidence to connect the kidnapping to any insurgent effort to influence British public opinion, insurgents have repeatedly attempted to do just that.

The kidnapping and ultimate execution of British engineer Kenneth Bigley earlier this month did indeed cause an uproar in Britain, with the government insisting until the end that it would not negotiate Bigley's release with terrorists.

CARE International is one of the world's largest independent global relief and development organizations. It operates in more than 72 countries in Asia, Africa, Latin America, the Middle East and Eastern Europe.

Hassan, who is married to an Iraqi, is a frequent guest on television news programs in the United States and around the world. "She sees herself as an Iraqi," a CARE spokeswoman told wire services. "Iraq is her home. She has been living there for many years and would never consider coming back to Britain," the spokeswoman said.

Since the U.S. invasion of Iraq, she has spoken often in interviews about the precarious situation for aid workers in the country.

"The status in Baghdad is a status of insecurity," she told CNN in May 2003.

Engineer Kenneth Bigley became the first British hostage to be killed in Iraq when he was beheaded by his kidnappers -- followers of the Jordanian militant Abu Musab Zarqawi -- earlier this month.

Barbash reported from Washington.