Twenty-one black current and former city police officers filed a discrimination lawsuit against the city, alleging that nooses were hung in their lockers, dog feces was placed on their desks and zebra stripes were painted on pictures of their mixed-race children.

The federal class-action lawsuit filed Monday accuses the department of condoning a hostile workplace, blocking black officers from promotion, levying uneven discipline and retaliating against officers who spoke out against discrimination.

It also alleges that racism led to the firing last month of former police Commissioner Kevin P. Clark (search). Mayor Martin O'Malley (search) said domestic abuse allegations against the commissioner, though unsubstantiated, had eroded his leadership ability.

The group of officers seeks financial damages, the appointment of an independent monitor and the reinstatement of fired officers, among other restitution.

City Solicitor Ralph S. Tyler (search) called the allegations "untrue" and said many claims are barred by statutes of limitations.

"People who have serious issues to raise come in to present them, they don't issue press releases," he said. "What I know in the short time I've had to look at it is that a large number of plaintiffs are people who have had what we call 'troubled' histories in the Police Department."

The lawsuit's accusations reach back to 1994.

City officials said Monday that since O'Malley took office in 1999, the percentage of African-American sworn officers has increased to 43 percent from 38 percent.

Clark, who is not a plaintiff in the suit, has filed a separate action against O'Malley.