Alexandria police said yesterday that they are investigating three similar incidents that occurred in recent weeks in Old Town, including one in which a couple was struck on the head with bricks in a possible robbery attempt.

"We don't know if they're related," said Amy Bertsch, a police spokeswoman. "They're similar in that the suspect approached the victims from behind, and they occurred in the same general area of Old Town. It's unusual to see this concentration of criminal activity in that area."

A 52-year-old man and a 54-year-old woman were walking in the 400 block of North St. Asaph Street on June 12 when they were attacked by two males, police said.

The couple were treated at area hospitals and released.

Four days earlier, a woman walking in the 500 block of North St. Asaph received minor injuries about 10:30 p.m. when she was struck on the head and her purse was snatched, police said.

On June 14, two men approached two women in the 100 block of North Fairfax Street about 11:30 p.m. and tried to steal a purse. They struggled, and the men fled.

Police ask that anyone with information call 703-838-4404.