An off-duty D.C. police officer was shot and seriously wounded last night in Northeast Washington, apparently by a uniformed D.C. officer who had mistaken him for an assailant, police officials said.

The off-duty officer, identified as Dwayne Washington, who police said joined the force about a year ago, was shot once in the chest and taken to Washington Hospital Center about 10 p.m. Officials there said he was in stable condition.

The shooting occurred near Bladensburg Road and New York Avenue NE, which is one the District's busiest intersections.

Lt. Reginald Smith, a police spokesman, said the off-duty officer was shot after being approached by uniformed officers who had seen him exchange gunfire with two other men near the intersection.

The officers ordered the off-duty officer to drop his gun, and as he turned toward them, one officer fired, Smith said.

Minutes before he was shot, the off-duty officer and his wife were disputing a traffic accident with two men near the corner of Montana and New York avenues NE, police officials said.

That led to a brief chase, then an exchange of gunfire, police and witnesses said.

The off-duty officer, they said, was on foot firing at the men as they drove away.

At that point, witnesses said, two uniformed officers who were parked in a police vehicle nearby raced to the scene.

"Two cops came over and shot at the guy who was shooting at the car," said one witness, who asked not to be identified.

According to the witness, the off-duty officer said, "Don't shoot, don't shoot, I'm a police officer," as one of the uniformed officers fired his weapon.

The names of the two uniformed officers were not available last night.

Police said they had arrested one man in connection with the traffic dispute that sparked the shooting and were searching for a second man last night. The name of the arrested man, who was taken to police headquarters for questioning, was not immediately available last night.

Police cruisers swarmed New York Avenue as a police helicopter hovered above and officers combed nearby railroad tracks for the second suspect.

Last night's shooting was the third time this year that a D.C. police offier has been wounded by gunfire.

Earlier this month, a 6th District officer was shot in the leg while scuffling with a drug suspect in a park near 42nd Street and Hunt Place NE.

Several months ago, a plainclothes officer from the 4th District was shot in the hand by a uniformed officer who saw him running with a gun in the 1400 block of Newton Street NW.

In that case, the uniformed officer also mistook the plainclothes officer for a suspect, officials said.