Lydia Ko is four shots off the early pace after her first round at the Canadian women's golf Open on the LPGA tour.

The world number five has opened with a one-under par 70 to be tied for 24th.

Ko mixed three birdies with two bogies to sit solidly in the pack on a tough opening day. The 20-year-old hit nine of 13 fairways and 12 greens in regulation, and required 29 putts to complete her round.

American Marina Alex leads on five-under par.