D.C. police are investigating the stabbing of a 53-year-old man during a robbery Friday night near his house in Northwest Washington -- an attack that police said might be connected to a similar assault last week in the same area.

Police said the victim was near his home just after 10 p.m. in the 5500 block of Broad Branch Road when he was approached by a man who asked a question.

The resident grew frightened and began to run, police said. The assailant caught him and stabbed him several times, police said.

The attacker fled with the man's wallet, police said. The victim, whose identity was not released because police consider him a witness, was taken to a hospital, where he was in serious but stable condition yesterday, authorities said.

Police said the attack was similar to one that occurred July 10, when a man in his seventies was walking in the 5200 block of Chevy Chase Parkway NW. About 9:15 p.m., the driver of a burgundy van stopped to ask the man for directions, police said.

The driver approached the victim and pulled out a knife, police said. The two men struggled for the knife, and the victim suffered a stab wound to his hand. The assailant fled with undisclosed items, police said.

Police said witnesses have reported seeing two vans, including a burgundy one, in the area of Friday's stabbing.

Police officials said investigators have not conclusively linked the two robberies.

They also said that detectives were looking into the possibility that the two attacks might be tied to a third stabbing and robbery July 8 in Northwest.

In that incident, authorities said, a man was stabbed and robbed by an unknown assailant, who followed him into his house in the 2200 block of 15th Street NW. The victim was critically injured but is expected to survive, police said. The assailant was seen driving from the scene in a brown or burgundy minivan, police said.

Detectives urged anyone with information to call 202-727-9099 or 202-282-0043.