Emile Heskey and Henrik Larsson both hit the net in their much-hyped comeback games.

It was the England international striker who came back to haunt his former manager Martin O'Neill to give Liverpool the upper hand in this UEFA Cup quarter-final tie.

But El Hadji Diouf soured the draw for the Worthington Cup winners late on when he appeared to spit into the Celtic crowd.

The news before kick-off that the Swede and his rival had recovered from a double fracture of the jaw and a hamstring injury respectively added further spice to the occasion.

Liverpool manager Gerard Houllier will be the happiest of the two managers after Heskey scored a vital away goal, and put them on course for the semi-finals, against the man who launched his career at Leicester City.

Amazingly it was only his seventh goal of the season compared to Larsson's 35th, but the winners of competition two seasons ago will be favourites to finish the job at Anfield next Thursday.

Heskey came in for Vladimir Smicer in the only change from Saturday's victory over Bolton Wanderers, but there was a surprise in Celtic's line-up with Paul Lambert dropping out to accommodate Chris Sutton in midfield and the prolific striker alongside John Hartson.

Celtic, chasing trophies on four fronts, were on a high after the weekend win over Rangers.

The Scottish champions took inspiration from the incredible noise generated by the home fans and were within inches of taking the lead inside the first 30 seconds.

Hartson beat Djimi Traore in the air and controlled Alan Thompson's pass before launching a fierce drive which beat Jerzy Dudek, but flicked the top of the crossbar.

Liverpool failed to heed that warning and Celtic capitalised to make a dream early breakthrough just over a minute later.

The usually dependable Sami Hyypia misjudged Stilian Petrov's cross and Hartson controlled the ball and lobbed it to the back post.

Thompson centred for Larsson to bundle the ball off his knee and past Dudek from close range.

The men from Merseyside responded with a weak effort from Danny Murphy after the midfielder won a challenge with Jamie Smith, and Robert Douglas comfortably saved.

But Celtic continued to bombard the Liverpool goal and Hartson sent another long-range effort over the bar after skipping past Dietmar Hamann in the fifth minute.

Liverpool started to settle down when Murphy fired over from outside the box after Michael Owen had stepped over Jamie Carragher's infield pass.

But they retaliated in the best way possible by equalising in the 16th minute when John Arne Riise threaded the ball through to Heskey to fire the ball low past Douglas and into the bottom corner of the net from a tight angle.

That clearly knocked the home side out of their stride and they suffered an injury blow in the 26th minute when Thompson had to be replaced by Steve Guppy.

But while the crowd have helped Celtic to go unbeaten in their last 10 European matches at Parkhead, they certainly worked against Celtic after Heskey's leveller, with every bad touch greeted by screams of frustration from the expectant supporters.

The home side looked to have recovered from that sucker-punch as they finished the half strongly.

Liverpool looked the more confident team after the restart, but just a minute into the half Hartson went down on the edge of the area under the clumsy challenge of Traore, but referee Terje Hauge waved away protests.

The visitors continued to look a major threat on the break and only some great defending by Bobo Balde stopped Owen wriggling free in the box.

Diouf then got on the end of Riise's free-kick, but his goalbound header was blocked by Joos Valgaeren.

Larsson had a glorious opportunity to put Celtic ahead once more in the 53rd minute when Hartson capitalised on a slip by Traore to send the Swedish star clean through on goal, but Dudek read his chip perfectly to push the ball behind for a corner.

The Glasgow side almost paid the ultimate price in the 62nd minute following the best move of the match.

Heskey's flick found Gerrard, who quickly sent Diouf away down the right.

He slipped the ball inside to the Gerrard who directed the ball wide of Douglas' post.

Moments later Balde needed to head Gerrard's fiercely struck drive clear after more good work by Traore on the flank.

Douglas then prevented Owen making it goals in five successive matches and equalling Ian Rush's European record when he brilliantly turned his right-foot drive around the post in the 75th minute.

Larsson was feeling the pace and was replaced by Lambert, while Petrov and Guppy were booked as they desperately tried to stop Liverpool from scoring.

Diouf appeared to spit in the direction of the Celtic crowd, sparking an angry reaction from a fan who was arrested.

The player was replaced soon after and given a police escort down the tunnel.

That could have spoilt a glorious night for Heskey and Liverpool, with Reds now favourites to move into the last four at the expense of the ex-Leicester striker's former boss.

Teams

Celtic: Douglas, Mjallby, Balde, Valgaeren, Smith, Lennon, Petrov, Sutton, Thompson (Guppy 26), Larsson (Lambert 76), Hartson.

Subs Not Used: Marshall, Sylla, McNamara, Maloney, Crainey.

Booked: Petrov, Guppy.

Goals: Larsson 3.

Liverpool: Dudek, Carragher, Hyypia, Traore, Riise, Murphy, Gerrard, Hamann, Diouf (Biscan 90), Owen, Heskey.

Subs Not Used: Arphexad, Baros, Smicer, Diao, Cheyrou, Mellor.

Goals: Heskey 17.

Att: 59,759

Ref: Terje Hauge (Norway).