Toronto police are investigating after a cyclist was critically injured in a collision early Sunday morning.

Police said the victim was struck by a vehicle on Bloor Street West, just west of Lansdowne Avenue, and rushed to hospital with life-threatening head injuries.

A Toronto EMS spokesperson said the victim is a man in his 20's.

The collision occurred at about 4 a.m.

Police said the cyclist was heading north on St. Helens Avenue and then turned into Bloor's westbound lanes, where he was struck by a westbound car, which was occupied by three people.

The driver stopped at the scene and waited for police to arrive, a police spokesman told CP24.

Because of a police investigation at the scene, Bloor was closed near Lansdowne until about 9 a.m.

Police continue to investigate to determine whether charges are warranted.