Celtic went five points clear at the Scottish Premier League summit with a hard-earned victory to sink 10-man St Johnstone 2-0 in farcical conditions at rain-soaked McDiarmid Park.

Joos Valgaeren put Martin O'Neill's men on their way to the points with a first-half header and Henrik Larsson bagged a late second with a penalty as they increased their lead over Hibernian and moved an impressive nine points ahead of defending champions Rangers.

The weather made conditions hazardous as the rain lashed down in Perth with both teams struggling to move the ball across the field which threatened to see referee John Rowbotham abandon the game midway through the second half.

But debutant Stuart Malcolm could not blame his dismissal on the conditions as he was ordered off near the end for elbowing Johan Mjallby, while he also gave away the free-kick for the visitors' opener.

Rowbotham may be wishing he could have called it off earlier in the day after upsetting both sets of supporters with some amazing decisions as he booked nine men as well as sending off Malcolm.

Celtic started as brightly as expected after the victory over St Mirren at the weekend and in just the sixth minute they had claims for a penalty.

Winger Bobby Petta, back after suspension, ran towards goal and he tumbled inside of the box under the challenge of Jim Weir, but referee Rowbotham waved away the protests.

Celtic continued to attack their opponents' goal and midfielder Paul Lambert went agonisingly close with a powerful free-kick which flashed just past the post.

The St Johnstone defence looked in all sorts of disarray early on and in the 22nd minute Momo Sylla and Alan Main left the ball for each other and luckily for the home side captain Weir was able to head clear Petta's dangerous cross.

Celtic continued to press and in the 28th minute Darren Dods made a desperate tackle on the edge of the box to prevent Swedish striker Larsson from getting a shot on target.

St Johnstone had Sylla and Weir booked as the driving rain made conditions difficult for both teams and Celtic also had Stilian Petrov shown the yellow card.

But the home side, who had conceded seven goals in their last two games, created their best chance in the 33rd minute and it was Gould who kept his side on level terms.

Evers played the ball to Gary Bollan inside the area, the full-back hit a fierce goalbound effort and the under-pressure goalkeeper made a low save to deny him.

Malcolm then came on for his first appearance in a Saints shirt for the injured Sylla and his opening contribution was to foul Petta on the left wing.

From the resulting free-kick the visitors took the lead in the 42nd minute when Alan Thompson curled in a left-foot cross for Valgaeren to rise in the box to head emphatically home for the first goal of his Celtic career.

The rain continued to fall, making the conditions almost impossible to play as puddles began to appear on the pitch.

It was bordering on the farcical but St Johnstone striker Kiegan Parker could not blame it on that after a reckless challenge on goal-scorer Valgaeren.

Moments later Main could not hold a low long-range effort from Thompson which trickled from his grasp, but fortunately for him no Celtic player was on hand to fire home.

Bollan became the next player into the book for a tackle on Agathe as the fourth official showed his concern at the state of the pitch.

Larsson should have sealed the points from the resulting free-kick when he rose to meet Thompson's in-swinging cross but he blazed his header just wide of the upright.

Parker then got away from the Celtic defence in the 69th minute and Gould's outstretched arm took it away from Evers to keep his side in front.

St Johnstone's frustration worsened in the 81st minute when first Main gave away a free-kick in the box after he handled Alan Kernaghan's pass back.

But they were about to face an even greater task as Malcolm's night was about to get even worse when he was red-carded for elbowing Mjallby at the back post and Kernaghan was booked for remonstrating with the referee.

Nothing came of that chance but in the 86th minute Celtic were awarded a penalty when Kernaghan brought down Petta inside the box and Larsson stepped up to send Main the wrong way for his 15th goal of the season.

Substitute Paul Hartley became the next man in the book for another bad tackle on Petta and Larsson was booked for handball as both sets of fans wanted the whistle blown to end an eventful if farcical night.

But for Celtic the three points were on their way back to Parkhead and they will be looking at going 12 points ahead of Rangers on Saturday.