Inbee Park two shots clear of Lydia Ko at women's Olympic golf in Rio

Inbee Park opened up a two-shot lead at the women's Olympic Golf, as world No 1 Lydia Ko fired a hole-in-one to charge up the leaderboard.

Park followed back-to-back 66s with a one-under 70 in tough scoring conditions in Rio, as Ko surged into contention earlier in the day with a bogey-filled 65. 

Ko is joined in a tie for second with Gerina Piller after the American posted a third-round 68, while Charley Hull slipped five strokes off the pace after a run of late bogeys. 

Beginning seven strokes adrift of Park, Ko followed an opening-hole birdie with successive gains from the fifth.

The New Zealander then aced the 140-yard eighth - the second player of the day to so after China's Xiya Lun - before a tap-in birdie at the ninth saw her reach the turn in 29.

A strengthening breeze made scoring more difficult along the back nine, where Ko completed every hole in regulation to set the clubhouse target at nine under.

Park, playing in the final group with Hull and Stacy Lewis, birdied three of his opening five holes but dropped shots after missing the seventh green in two and two-putting the ninth from eight feet.

Hull's mixed start saw her fail to get up-and-down from a bunker at the fourth but birdie the following two holes, only to drop shots over the next two.

The pair both picked up a stroke at the 10th, with Hull's coming from 20 feet, before Park saw her lead grow to three strokes when Piller bogeyed the 12th.

Park saw her lead shrink when she failed to save par from 10 feet at the 12th and failed to get up-and-down after missing the 14th green.

The world No 2 restored her three-stroke cushion by adding a fifth birdie of the day at the 16th and draining a 20-footer at the next, only to give a shot back with a bogey-six at the last.

Shanshan Feng lies one stroke outside of the medal places on eight under, while four bogeys over the final seven holes leaves Charley Hull a further two shots back with Korean pair In Gee Chun and Hee Young Yang.

Irish amateur Leona Maguire slipped down the leaderboard after a back-nine 41, with Britain's Catriona Matthew now over par for the week after a third-round 77.