ANNAPOLIS Md. (Reuters) - Maryland police early on Friday killed a 20-year-old man armed with a pellet gun that officers mistook for an assault rifle, a police spokeswoman said.

The officers had responded at about 2 a.m. EDT to a dispute between two men, one of them holding what officers thought was an assault rifle.

The Prince George's County Police officers opened fire outside a Suitland, Maryland, apartment complex when the man refused to drop his weapon, spokeswoman Julie Parker said.

After several warnings to put down the gun, both officers shot and killed the man, Parker said.

The officers have been placed on administrative leave, pending further investigation. The dead man has not been identified.

Police found a pellet rifle and a pellet pistol at the scene. It is not known if drugs or alcohol were involved, Parker said.

She said the shooting and police response to what turned out to be a pellet gun had drawn some criticism on Twitter and other social media.

"You're talking about a very realistic weapon," she added.

(Reporting by John Clarke; Editing by Ian Simpson and G Crosse)