Leigh Griffiths, the Celtic striker, has criticised referee Serhiy Boiko for disallowing his late goal against Astra Giurgiu and accused the Ukrainian official of laughing as he made the contentious decision.

Griffiths had already begun to celebrate what he was convinced would be the decisive strike in Romania only for Boiko to award a free-kick for a foul on Cristian Oros.

The Astra defender had tumbled while attempting to clear the initial cross under pressure from Griffiths, before the forward poked the loose ball into the net with just seven minutes remaining. However, Celtic were left with only a 1-1 draw after Stefan Johansen's first-half opener was cancelled out by William de Amorim late in the match.

With Red Bull Salzburg securing a comprehensive victory against Dinamo Zagreb last night, Celtic would have progressed to the knockout stages of the Europa League had Griffiths' goal stood. Instead the Scottish champions require two points from their remaining two matches in Group D to reach the round of 32, adding to Griffiths' frustration.

"I have watched it back [on TV], everybody in the changing room has watched it back, and they said it's not a foul," said Griffiths, whose side are second behind Salzburg in the group standings. "I knew it wasn't a foul. I just stood my ground and the boy jumped into me.

"I read where the ball was going to go and I knew that he'd jumped awkwardly and was going to fall backwards. The ball fell to my feet and I put it away. The ref didn't even blow straight away. He let me go away and celebrate, then brought it back and started laughing about it. It seemed like every foul he gave against us he started laughing.

"I can't believe he has given a foul for that. I've watched it back three or four times and so has the manager and everyone else, and they've all said it's not a foul. It's just one of those things and, in our next game, we've got to take three points to get through the group stages."

The decision to disallow Celtic a second goal was also challenged by Ronny Deila. The Celtic manager had not been certain that the match would go ahead at all as heavy fog enveloped Giurgiu, forcing the match to be delayed. The game was played out in poor visibility but Deila was adamant afterwards that he had seen been no obvious infraction committed by Griffiths.

"Everybody who has seen it again says it should be a goal. Leigh said he didn't do anything, so we should have won 2-1," said the Norwegian. "Sometimes that happens and we have been lucky some other times. This time it has gone against us."

If Celtic are able to secure a win against group leaders Salzburg when the two teams meet in Glasgow later this month then Deila's side will still progress to the knockout stages of the competition. Yet the Celtic manager reiterated last night that his players should not have to wait.

"I think we deserved to win. It was two points lost," said Deila, whose side finished the match playing against 10 men after Astra's Vincent Laban was sent off for a lunge on Charlie Mulgrew. "We were the best team tonight, in the first half we were excellent and scored a nice goal. In the second half we controlled it quite well but they scored a fantastic goal.

"We had enough chances to kill the game. But in the end we have one point and, while I am not happy with that, it is better than nothing."