A suspect is under arrest after slashing a man in the head with a machete before throwing an improvised explosive device at an unmarked police vehicle in Queens, lighting it on fire, police officials said.

In what is believed to be a random act of violence, the suspect, whom police had not identified as of press time, attacked the victim at about 5:30 p.m. yesterday with a machete as he was walking by a building on 123rd Street in Richmond Hill, police said.

The victim, who sustained a laceration to the head, fended off the suspect with an umbrella before the suspect fled into 86-23 123rd St., police said.

Shortly afterwards, a patrol of plainclothes police officers arrived at the scene.

As they began canvassing the block, the suspect flung a homemade explosive device from a perch atop the roof of the building at their unmarked vehicle, causing it to go up in flames, police said.

Before the suspect was finally arrested at about 7:15 p.m., he launched a total of five of the improvised explosive devices as he traveled between several neighboring rooftops, police said.

A team of highly trained emergency service officers negotiated themselves close enough to the suspect to make the arrest, police said.