BAGHDAD, Iraq, (AP) -Gunmen in Iraqi army uniforms staged a mass kidnapping on Sunday at the office of the Iraqi Red Crescent in downtown Baghdad, police said.

An official of the Iraqi aid group said the assailants abducted 20 to 30 employees and visitors, but left women behind. The official spoke on condition of anonymity because of security concerns.

Police, however, said they did not know how many people were kidnapped at the office in Andalus square. They said the gunmen arrived at the office in five pickup trucks.

The Red Crescent, which is part of the international Red Cross movement, has about 1,000 staff and some 200,000 volunteers in Iraq. It works closely with the International Committee of the Red Cross, which visits detainees and tries to provide food, water and medicine to Iraqis.

Several mass kidnappings have been carried out in the Iraqi capital in recent months, possibly by armed groups on either side of the sectarian conflict between Sunnis and Shiites.

On Thursday, gunmen in military uniforms kidnapped people from a commercial area in central Baghdad, police said. The attackers drove up in about 10 sport utility vehicles and began rounding up shop owners and bystanders. Police said 50 to 70 people were abducted, but at least two dozen were later released.

Last month, gunmen in Interior Ministry commando uniforms abducted scores of men from a Higher Education Ministry office building. The Education Ministry is predominantly Sunni Arab. About half of the victims were released.