Sean Bell was killed and two of his friends wounded in a 50bullet barrage as they left Bell's stag party at a strip club in the Queens area of New York.

Lawyers for Marc Cooper, Gerscard Isnora and Michael Oliver said their clients had been indicted, but they did not know what offences they had been charged with.

Five New York City officers were involved in the incident, but the three who will face charges reportedly fired the most shots.

Cooper fired four shots;

Isnora, 11; and Oliver, 31 - in the 25 November confrontation that killed the 23-year-old. The shooting stirred outrage around New York City and led to accusations of racism against police.

Bell was black, as are two of his friends who were injured in the shooting. Cooper and Isnora are black. Oliver is white.

District Attorney Richard Brown said that the grand jury had reached a decision and it would be announced on Monday. He gave no reason for the delay, but indictments are often kept sealed until lawyers and their clients are notified and arrangements can be made for the defendants to surrender.

The case also brought back painful memories of other infamous police shootings in New York City, including the 1999 killing of unarmed African immigrant Amadou Diallo, who died in a hail of 41 bullets.

The officers in that case were acquitted of criminal charges.

Police union officials defended the officers, arguing they were responding to reasonable suspicions the victims were armed and dangerous.

"This indictment sends a chilling message to all New York City police officers and to all law enforcement agents throughout the country, " said Michael Palladino, president of the Detectives' Endowment Association. "You can act in good faith and there is no margin for error."