Liam Johnston shot the best round of his European Tour career on Thursday with a 10-under par 61 that put him top of the leaderboard at the Portugal Masters.

Johnston, 27, shot 31 on the front nine of his first round before firing five birdies in his next seven holes to set up a near-perfect score and sit one shot ahead of Frenchman Julien Guerrier, who also had his best day on the tour.

"My game feels as it is really trending in the right direction and, more importantly, I have really improved mentally," said Johnston, who is yet to win on the European Tour.

"I wouldn't say I felt a round like this has been coming, but I have been playing well."

The Scot's round on a low-scoring day at the Dom Pedro Victoria course in Vilamoura beat his previous lowest score on the European Tour by six shots.

Englishman Laurie Canter is third at seven-under with Northern Ireland's Jonathan Caldwell a further shot back.