Playing football that at times verged on the continental, Celtic left themselves on the edge of Champions League qualification last night.

First-half goals from the wingers Bobby Petta and Didier Agathe in the seventh and 20th minutes gave Martin O'Neill's inspired side the perfect opening and, although Ajax pulled one back through Shota Arveladze close to half- time, Chris Sutton restored Celtic's merited advantage with a great header 10 minutes after the interval.

Sutton's was an imposing performance, yet he was over shadowed by Neil Lennon. If the latter is in similar form in the return then Ajax's hopes of a fightback are already forlorn.

During the afternoon there were looks ranging from dismay to amusement from the locals at the green tribe that had colonised the city centre. But there was little hint of the sporadic, unpleasant scenes outside the ground later, when Celtic and Ajax fans clashed on the stairs into the stadium. The Dutch police held off initially and it was the stewards who bore the brunt of the fighting.

The trouble did not appear widespread, though once inside the Amsterdam Arena the looks of dismay and amusement continued. At least this was at the football.

Petta was at the centre of these, much as he has been throughout his two years at Parkhead. When John Barnes brought him from Ipswich in 1999, it was to a background of "who?" Petta subsequently lived down to all expectations.

Under O'Neill, however, Petta has blossomed, to the extent that he is a certain starter every week. Thus he was encouraged by O'Neill to forget the knee injury that restricted him against Kilmarnock last Saturday to 18 minutes. How quickly they felt the benefit of that decision.

It had been an understandably tentative beginning, and when Lennon played a seventh-minute pass into the feet of Sutton, few expected little more than a safe lay-off. Sutton instead turned and hit a fairly weak, curling shot. It seemed soft enough for the Ajax goalkeeper Fred Grim to catch but he chose to punch.

Grim miscued. The ball fell conveniently to Petta who, from a narrowing angle, beat the goalkeeper.

A dream opening, and 10 minutes later things almost got better for Celtic.

Agathe, like Petta having a fine game on the opposite wing, swung in a corner that Henrik Larsson met first. The ball flicked off Larsson's forehead, struck the bar and dropped to Sutton. He just failed to make the connection that would have given Celtic a two-goal lead.

Stunned, Ajax took a while to respond, but Robert Douglas was forced into a sturdy block from Mido, and five minutes before the interval the Dutch pulled a goal back. Douglas was again asked to make a save. Again he did so, from Nikos Machlas, but the rebound landed at the feet of Arveladze and the Georgian does not miss from seven yards.

There was still time before the interval for a superb Celtic move featuring Lennon, Joos Valgaeren, Larsson and Sutton to bring a brilliant save from Grim.

Celtic derived deserved confidence from that and displayed it on the re-start when Larsson nearly scored immediately after a flick from Sutton.

In the 54th minute Sutton delivered what should be the tie's decisive blow. Lennon won possession in midfield. From there the ball was ferried to Agathe via Sutton and when Agathe's tempting cross came in, Sutton met it on the run from six yards. With Grim nowhere the ball cannoned in off the bar.

AJAX: Grim; Chivu, Trabelsi, Mido, Arveladze, Pasanen, Machlas,Yakubu, Van der Vaart, Ikedia, Cruz.

CELTIC: Douglas; Boyd, McNamara, Valgaeren, Larsson, Sutton,Lambert, Petta, Agathe, Lennon, Mjallby.