BOSTON -- A man who attacked a woman on the Esplanade in July has been forensically linked to two other unsolved attacks, police said Tuesday.

"In the past few days, the Massachusetts State Police Crime Laboratory has made a forensic link between not only the two Esplanade attacks, but also a link to a previously reported sexual assault in South Boston in July 2006," said Massachusetts State Police Superintendent Mark Delaney.

A woman was abducted at knifepoint on Beacon Street in Boston and forced to walk to the Esplanade, where she was sexually assaulted and subsequently robbed on July 29 at about 4 a.m., police said.

The man also took the victim's cell phone, camera and money.

Police said that was the same man who attacked a female jogger in June and sexually assaulted her along the Esplanade. The attacker was also linked to a July 2006 attack on a woman in South Boston, police said.

Police released a sketch of the attacker last week. They described him as a black man, 28 to 32 years old, 5 feet 10 inches tall, about 220 pounds with a muscular build and a shaved head. The man was wearing a sleeveless T-shirt and dark-colored jeans.

State and local police urge residents to use caution.

"The females were usually approached from behind, they were then either forced to go to a desolate area or a deserted area or one of the local alleys or areas within the vicinity where the assault actually occurred," said Massachusetts State Police Sgt. Brian Howe.

Anyone with information about the man or incident should contact the State Police Barracks in Boston at 617-727-6780.