A pedestrian and a motorcyclist suffered serious, life-threatening injuries as a result of collision on Yonge Street, about a block south of St. Clair Avenue, police say.

Crash at Yonge Street and Pleasant Boulevard

A collision involving a motorcycle and a vehicle at Yonge Street and Pleasant Boulevard sent both a pedestrian and a motorcyclist to hospital on Sunday. (CBC)

Toronto police Sgt. Paul Strangways told CBC Toronto that three motorcyclists were heading north on Yonge Street, approaching Pleasant Boulevard, just before the crash occurred on Sunday.

Strangways said that at the same time, a vehicle was making a left-hand turn from the southbound lanes of Yonge Street.

"He may or may not have been able to see the motorcyclists coming," he said.

"As he made his turn, he clipped one of the three motorcyclists."

Strangways said that the motorcycle then lost control and went onto the sidewalk on the east side of Yonge Street, striking a pedestrian.

He said that the motorcyclist and pedestrian were rushed to hospital.

The collision remains under investigation, but Strangways said witnesses have indicated that the three motorcyclists were driving in "an aggressive manner" prior to the crash.