Gunmen dragged 24 people, mostly teenage students, from vehicles and shot them dead in a small town north of Baghdad on Sunday, police said.

The abductions in Baghdad in broad daylight showed how far Maliki has to go to establish law and order three years after a U.S.-led invasion toppled Saddam Hussein.

Three suspects in the kidnap and murder of Iraqi-British aid worker Margaret Hassan in 2004 were going on trial in Baghdad on Monday, a British official said.

Iraqi judicial officials were not immediately available for comment on what was believed to be one of the first, if not the very first, known trial for the abduction or killing of a foreign-born civilian in Iraq.

Hassan, an Iraqi-British national who had lived in Iraq for more than three decades after marrying an Iraqi engineer, was head of the Iraqi operation of the CARE International charity.

She was abducted while traveling to work in Baghdad in October 2004, and was killed about a month later after appealing in video messages made by her abductors for British forces to withdraw from Iraq.

No group claimed responsibility for the abduction or the killing, and her body has not been found.

Kidnappings are still a major part of the security crisis.

Gunmen killed a Russian embassy employee on Saturday and kidnapped four others in Baghdad.

In Baghdad's heavily guarded Green Zone, ousted Iraqi president Saddam Hussein and seven co-accused returned to court to face charges of crimes against humanity in the killings of 149 Shi'ites in the early 1980s.