The assailant approached his victims from behind on Northwest Washington streets. He grabbed women at random and stabbed them with a sharp object before running off when witnesses responded to the victims’ screams.

D.C. police are searching for a man they believe is responsible for four assaults that have occurred in the past seven weeks during late-night and early-morning hours as the victims walked alone, Chief Cathy L. Lanier said at a news conference. None of the victims suffered life-threatening injuries, Lanier said, but she urged women in Northwest to take precautions.

“We are asking that until we identify and apprehend this person that women try to have someone with you if you’re out in the late evening hours and be aware of your surroundings,” Lanier said.

Police said there was no clear motive and none of the women were robbed. Three of the attacks happened in the Petworth neighborhood, but there seem to be no similarities between the victims, Lanier said.

The first woman was attacked as she got out of her vehicle in the 400 block of Emerson Street about 11:15 p.m. on May 5. The attacker walked up and began to stab her without warning, officials said. The victim raised her arm in defense and he cut her forearm and hand and scratched her torso.

The next incident happened June 10, as a woman opened the gate to a home in the 1300 block of Decatur Street about 10:30 p.m., police said, and the assailant stabbed her in the torso and arm.

Three nights later, just after midnight, a woman was attacked in the unit block of Adams Street. The attacker tried to put her into a headlock before he cut her arm, police said.

Just after midnight Wednesday, a woman was tackled by a man in the 1100 block of Allison Street. She screamed and fought him off but suffered minor cuts.

Victims told police the man is a slim, athletically built light-skinned black or Hispanic male with short brown hair who is between 5-feet-8 and 6-feet-1 tall.