BAGHDAD, Iraq (CNN) -- Iraqi and U.S. forces found belongings of kidnapped CARE worker Margaret Hassan and arrested three people in connection with the case, officials said Sunday.

A handbag, ID and clothing that belonged to Hassan was seized during a raid in a Baghdad suburb, Iraqi police said.

The three suspects were among those apprehended in the overnight raid, British Embassy spokesman Martin Cronin told CNN.

Hassan, former director of the humanitarian organization CARE in Iraq, is a British citizen who was taken hostage in October. A video purportedly showing her being shot to death surfaced about a month later on the Arabic-language Al-Jazeera satellite television channel.

"We believe this is the first evidence that's been found regarding her since her death," Cronin told The Associated Press.

Some of the people who were detained acknowledged taking part in killing Hassan, Reuters reported.

Hassan, 59, Irish-born and with dual British and Iraqi nationality, was seized by gunmen on her way to work in western Baghdad. (Full story) Baghdad attacks

At least 13 Iraqis were killed and 12 were wounded in three attacks in Baghdad on Sunday, Iraqi police said.

A suicide car bomber targeted a U.S. military convoy in the southeastern district of al-Za'faraniyah, killing five Iraqi civilians, including a 5-year-old. Iraqi police said the car bomb also wounded twelve people. There was no immediate word about U.S. casualties.

In southeastern Baghdad, five Iraqi police officers were killed in a battle with about 30 insurgents at a police checkpoint, Iraqi police said. Insurgents used small arms to launch their attack, which occurred in the al-Rustumiya neighborhood, police said. After the battle, the insurgents took weapons from the bodies and fled, police said.

In another attack, gunmen killed Ahmed al-Lu'aibi, director general of Baghdad's al-Mansour sewage facility and two of his guards, Iraqi police said. The drive-by attack happened in the al-Jihad neighborhood of western Baghdad, police said.