Police are seeking the public's assistance in apprehending a man wanted for sexually assaulting four women in their apartments in Northwest Washington, three of them in the last four months.

The suspect, who is between 30 and 40 years old, reportedly wears a dark mask with cutouts for the eyes and mouth, dark clothing and dark gloves.

In all four instances, the man entered the apartments through an unlocked window or one easily forced open, police said. He was armed with a knife.

All four attacks occurred between 3 and 5 a.m. They took place in the Glover Park, Foxhall Village and Palisades neighborhoods of Northwest Washington.

The first attack was Sept. 17, 1989, in the 2300 block of 41st Street, and the second 13 months later, on Oct. 23, 1990, in the 4100 block of W Street NW.

Since the October 1990 attack, police believe, the suspect has assaulted two other women. Both of those incidents were on MacArthur Boulevard, one on Dec. 3 in the 4800 block, the other on Jan. 26 in the 4500 block.

Police released information on the assaults and a description of the assailant in the last week of January.

As of yesterday, police had reported no arrests in the case.

The suspect is about 5 feet 8 inches tall and weighs about 190 pounds. Anyone with information is asked to call the sex crimes unit at 202-727-4151 or the confidential crime-solvers hot line at 202-393-2222.

If a tip received through crime-solvers results in the arrest and indictment of a suspect, the person who provided the information could receive up to $1,000.