Leigh Griffiths and Patryk Klimala came off the bench to score in the dying minutes as Celtic left it late to move top of the Scottish Premiership with a 2-0 win at St. Johnstone.

The Scottish champions go two points ahead of Rangers, who host Ross County later on Sunday, ahead of the first Old Firm derby for 10 months when the sides resume after the international break in two weeks' time.

For a long time it looked like Neil Lennon's men would have to settle for a point in Perth as they had just one shot on target until the 90th minute.

Despite Celtic's dominance in possession, St Johnstone had come closest to scoring when Craig Conway hit the post early in the second-half.

Lennon emptied his bench in the search for a winner, making five substitutions.

Griffiths was introduced for his first appearance of the season after being publicly criticised by his manager for returning to pre-season overweight.

However, the Scotland striker showed he maintains his predatory instincts in the box as he headed in Hatem El-Hamed's cross as the game entered stoppage time.

"Delighted to be back involved," said Griffiths. "For me personally it's about getting fit.

"The game is 90 minutes long, we know we are going to have chances. It didn't come till the 90th minute but two goals again, a clean sheet and we move on."

Moments later, Klimala's persistence was rewarded with his third goal of the season as he bounced back to his feet after being wiped out by Liam Gordon to slot high past Zander Clark.