Two serial carjackers are targeting drivers in Southeast and Northeast Washington by rear-ending vehicles and driving off after the victims get out to assess the damage and exchange information, D.C. police said.

The tactic — which police call a “bump and run” — has been used four times since Aug. 28. The bandits were successful three times; in one case, police said the victim stayed in her car and the would-be robbers fled.

No weapons have been used, but police said that one woman was slightly injured when a carjacker pushed her out of the way to get to her vehicle. In each case, police said, the driver had left the keys in the ignition and the motor running.

Cmdr. George Kucik, head of the D.C. police criminal investigation division, said that drivers who are hit from behind should lock their doors, stay in their vehicles and dial 911. “We don’t want people hurt trying to save their cars,” he said.

Kucik said descriptions of the carjackers were vague — men in their 20s, one with long dreadlocks — and he said police have recovered one of the stolen vehicles. He would not say whether detectives think that the carjackers are part of an organized ring or are taking cars for joy rides.

The latest theft occurred about 8 a.m. Thursday at Hartford Street and Alabama Avenue SE. Police said a silver vehicle, possibly a Buick, rear-ended a car. When the driver got out, police said, one of the men jumped in and drove off. His accomplice then followed.

Two incidents occurred Tuesday. Police said the first happened about 9:45 a.m. at Division and Eastern avenues NE. About a half-hour later and three miles away, police said, the carjackers used that victim’s Toyota Avalon to rear-end a car at Fort Davis Drive and Massachusetts Avenue SE. Police said that driver did not get out of her car.

The first carjacking that police have linked to the men occurred about 7 a.m. Aug. 28 at Alabama Avenue and Naylor Road SE.