Celtic manager Neil Lennon has warned fans that they can no longer 'cross the line' as the club faces more disciplinary action over their supporters' behaviour.

The Scottish giants were accused of letting off fireworks during their Champions League match against Cliftonville on Wednesday, prompting them to issue a statement threatening to close a section of the home ground that houses the 'Green Brigade' fans group.

Lennon concedes that the atmosphere created by that section adds a lot to the stadium, but insists that they must abide by the rules if they want to keep on attending.

"It's disappointing and it's not for the first time. Our motivation on this is health and safety - the safety of supporters," Lennon told reporters. "People look as though they enjoy themselves and they do add a lot to the stadium, I have been very vociferous in my support of that section in particular.

"But there are things they cannot do. We are not being over-critical but there are lines to be drawn and they can't cross them any more. I'm not a big fan of fireworks. I'm not a big fan of flares being let off in a crowded area.

"It doesn't do the players any good, it stops the game. It's just not necessary. You can still go to the game and enjoy it without having to light the place up as it were. They can light the place up in many ways, and they normally do that through colour and singing their songs."

Celtic beat Cliftonville 5-0 on aggregate and will now face Elfsborg in the next qualifying stage.