Police yesterday said a woman's car was also pierced with a long- bladed knife shortly after it had been used to cut a motorist's arm just after midnight on Sunday.

The woman, who had been performing a U-turn, quickly took off away from the two men, police said.

The two men were involved in an earlier incident after a motorist stopped to speak to them believing they had thrown rocks at his car.

As the driver was getting out of his car one of the men walked up and slashed his arm.

The 27-year-old, of Kings Meadows, left the scene before being taken to the Launceston General Hospital.

The man required surgery to repair tendon damage.

The incident occurred at the intersection of Hobart Road and Nunamina Avenue, Kings Meadows.

Shortly after this the woman's car was attacked in the same area.

A member of the public in another car attempted to follow the men but they could not be located.

Launceston CIB acting Detective Inspector Johnathan Higgins said it was an unusual and worrying incident.

He urged victims to contact police rather than get involved in dangerous situations themselves.

"You don't know what to expect if you decide to confront people ... it's better to report to police than dealing with it yourself," he said.

Launceston CIB is appealing for witnesses who may have seen two men, believed to be aged between 18 and 25, loitering around the Hobart Road area. One man is believed to have been wearing a red T-shirt and to have been carrying a long-bladed knife.

Both have been described as caucasian.

Anyone with information is asked to contact Launceston CIB on 6336 3910 or Crime Stoppers on 1800 3330 00.