Four men have been injured by a lightning strike on a golf course north of Toronto, with one man in critical condition, police say.

York Regional Police said all four golfers were taken to hospital after the incident on Tuesday morning.

Three are reported to be in stable condition. The critically injured patient, who police say is a 60-year-old man from Richmond Hill, was transferred later in the day to Sunnybrook Hospital in Toronto.

Emergency personnel say the four men hit by lightning were located about 200 metres from the golf course clubhouse. (CBC)

The other injured parties are a 51-year-old Thornhill man, as well as two Toronto men, ages 53 and 56.

Police said they received a call at 11:39 a.m. ET about the incident at Rolling Hills Golf Club in Whitchurch-Stouffville, Ont.

Witnesses say the lightning strike occurred on the 18th hole as golfers were taking their clubs into the clubhouse.

Peter Epstein told reporters that he saw a flash and heard a bang.

"You knew it was close," he said.

Epstein was among golfers at the course that tried to help the injured people.

He said one of the injured parties was without vital signs, but was revived by an ICU nurse who happened to be on the course.

Epstein said that man had burns and some of his clothes had melted.

"His hat was just melted, it was just completely blown off his head," he said.

Const. Andy Pattenden told CBC News that the golfers were injured about 200 metres from the clubhouse.

Other golfers were cleared off the course after the lightning strike.

Rolling Hills has yet to issue a statement.