Armed men abducted a top official of the charity agency CARE outside her Baghdad office Tuesday morning.

The abduction of Margaret Hassan, CARE International's head of operations in Iraq, was confirmed by the organization. But CARE offered little information beyond the facts widely known about Hassan: She was born in Dublin and has been in Iraq for 30 years, the past 13 of them working to bring clean water and health care to the country's poorest citizens.

"We're not saying anything further because we don't know who she was abducted by, or why, so we don't know what might be harmful to her," said Lurma Rackley, public relations director in the charity's Atlanta office.

[CARE International suspended its operations in Iraq following Hassan's kidnapping, the head of the agency's Australian arm said Wednesday, according to the Australian Broadcasting Corp.]

No individuals or groups have asserted responsibility for the kidnapping. By Tuesday afternoon, al-Jazeera satellite television was repeatedly airing a grainy, silent video that showed Hassan perched on the corner of a sofa, appearing alarmed. The video also showed a close-up view of several of Hassan's identification cards.

Her colleagues said the kidnapping slashed a deep gouge in the fabric of civil society here. Hassan, a naturalized Iraqi citizen who also holds British citizenship, has long been a bulwark of Iraq's beleaguered humanitarian community, widely respected for her generosity and renowned for her stubborn devotion to the country's poor.

In two wars, Hassan, who is about 60, remained in Baghdad when the bombs fell. She vocally opposed the international sanctions imposed on Iraq after its invasion of Kuwait in 1990, and she traveled widely before the U.S.-led invasion of Iraq in March 2003 to warn of the harm it would cause the country.

Hassan declined to leave her station a year ago when car bomb attacks began to strike humanitarian organizations, leading nearly every other international aid group to abandon Baghdad. And when kidnapping became widespread in and around the city, she continued to rise early each morning to go to the west Baghdad office of CARE, where her abductors found her at 7:30 a.m. Tuesday.

Since April, more than 150 foreigners have been kidnapped in Iraq. About 35 are known to have been killed, and many more are believed to be held captive. Before Hassan's abduction, seven women were known to have been kidnapped, and all were eventually released.

Abductions have been carried out by a variety of groups, principally criminal gangs seeking ransom, insurgents intent on demonstrating the inability of Iraq's interim government to provide security, and Islamic guerrillas who have seized -- and often beheaded -- Westerners and Iraqis who work with them. In every case, security experts warn, the greatest danger is that kidnappers will exchange a captive for cash in an underground marketplace where buyers include Sunni Muslim extremists.

"Ninety-nine percent of what's driving it is money," a U.S. official who works full time on kidnappings in Iraq said before Hassan's abduction. "The group that takes you is going to try to sell you up the chain for money, and if you end up with a political group, things aren't going to look good for you."

Hassan came to Iraq three decades ago after meeting her husband, Tahseen Ali Hassan, an employee of Iraqi Airways, in London. She joked about marrying into a strict Muslim family, friends said, but was especially close to her father-in-law, a physician.

One Iraqi friend recalled that Hassan's first job in Iraq was reading the news in English on state television. She joined CARE in 1991 after years as a fixture at the Baghdad office of the British Council, a cultural center attached to the British Embassy.

The ID cards displayed on the video sent to al-Jazeera documented her mixed identity: a Visa credit card in English, a shopping card in Arabic and a wallet-size laminated card issued by CARE listing talking points for "Media Interviews."

"She deserves every bit of respect that's been given to her," said Kathy Kelly, co-coordinator of Voices in the Wilderness, a group that visited Baghdad frequently in the late 1990s to protest the international sanctions that many aid workers said were hurting not the government of Saddam Hussein but Iraq's poor, especially children.

"There was a very steadying sense talking to Margaret," Kelly said. "She wasn't someone who ever tried to call attention to herself or pull rank on anybody because she had more experience than anyone else in Iraq.

"There was also that kind of stunning determination to remain in Iraq no matter how conditions were."

In London, British Prime Minister Tony Blair pledged to help secure Hassan's release.

"This is someone who has lived in Iraq for 30 years, someone who is immensely respected, someone who is doing her level best to help the country," Blair said. "It shows you the type of people we are up against, that they are prepared to kidnap somebody like this."

Elsewhere in Iraq on Tuesday, five members of the Iraqi National Guard were killed and 80 injured when mortar shells rained down on a base in Mushahidah, north of Baghdad, as about 550 guardsmen gathered in front of the main building.

Lt. Col. Waleed Mohammed Mashhadani, who said the base had been the target of several mortar attacks, said the shells fell from close by. U.S. helicopters raced to evacuate the most seriously wounded, but many Iraqis who live near the base refused to lend assistance.

"I saw some of the National Guards come out bleeding and asking for help," said Saber Ghanim, 23, who owns a tea stand near the front gate of the base. "No one helped them except a minibus driver who stopped and took some of them. They deserved that, because they treat us worse than the Americans."

Ghanim and others complained that the guardsmen raid private homes almost daily, humiliate people at checkpoints and accuse residents with the long beards uncommon in Iraq of being terrorists or Wahhabis -- adherents to the conservative strain of Sunni Islam, Osama bin Laden among them.

Jasim Mohammed Abbas, a guardsman wounded in the back and arm by shrapnel, vowed revenge. "This makes us more willing to continue," he said. "And we will give those Wahhabis a lesson they'll never forget."

A pre-dawn mortar attack on a U.S. base in Baghdad killed an American civilian working for the defense contractor KBR, the Associated Press reported.

Special correspondent Bassam Sebti in Mushahidah contributed to this report.

Margaret Hassan, CARE International's head of operations in Iraq, in an image from a video made in May 2003. She joined the aid agency in 1991.An Iraqi guardsman patrols outside his base in Mushahidah, north of Baghdad, after a mortar attack killed five Iraqi National Guard members and injured 80.