WASHINGTON >> A man swung a large ax at a District of Columbia police officer in an unprovoked attack early Friday, and the officer suffered a minor injury while struggling with the man, who escaped on foot, police said.

The officer was sitting in a marked police car when the man used the ax to shatter the driver’s side window, said Police Chief Cathy Lanier, who described the attack as an ambush.

Lanier stressed that police had no evidence linking the attack to any broader plot or to last week’s attack of a group of New York City police officers by a hatchet-wielding man, which New York’s police commissioner called an act of terrorism.

Lanier said police weren’t ruling out that possibility.

“A lot of these radical organizations, terrorist organizations are very vocal about targeting first responders. It’s no secret. It’s not new. But it certainly has ramped up,” Lanier said. “We’re on extremely high alert.”

Lanier said she spoke with John Miller, New York City’s deputy commissioner for intelligence and counterterrorism, to go over any investigative details that might be helpful.

The officer spotted the man briefly before the attack and believed he was carrying a baseball bat, Lanier said. The officer drove into an alley in an attempt to follow him but did not see the man again until the ax hit the car, Lanier said.

The officer chased the man and tackled him and was injured in the struggle, police said.

Police don’t have a good description of the man, and Lanier said investigators were pursuing 30 to 40 leads, including some generated by tips from the public. The FBI offered help with the investigation if needed.