Liverpool surged into the last 16 of the UEFA Cup with the sort of rewarding display which will lift the pressure from manager Gerard Houllier.

Houllier's much-maligned team produced a display of goals and thrills to further mend the wounds of a season of criticism which culminated in a death threat to the Anfield boss.

But on a freezing night in Bulgaria, the Frenchman looked warm and content - and his applause and clenched fist salute to the massed ranks of the visiting fans at the end of his 50th European game of his Anfield career spoke volumes.

Houllier had to try and guide Liverpool safely through the second leg of this UEFA Cup third round match with his team two goals to the good from the Anfield opener.

It was always going to be a tough task, despite the first leg scoreline, because Eastern Europeans on their own turf are a very different proposition.

Liverpool got the usual intimidation with smoke bombs and passionate singing on Bulgaria's national day, - when they celebrate Vassil Levski - the Sofia club is named after him - for his revolutionary zeal against the Turks.

All this national and club pride just heightened the tension for an unpredictable Liverpool who could just as easily grow as buckle under the pressure.

What Liverpool needed was a quick strike to deflate their hosts, and it came on six minutes from the man on whom they have grown to rely so much.

Skipper Steven Gerrard anticipated a back pass from Ilian Stoyanov and raced into yards of space before rounding goalkeeper Dimitar Ivankov and sliding the ball home from an acute angle.

The visitors doubled their advantage five minutes later when Harry Kewell's angled ball from midfield was chased by Michael Owen.

The England striker sprung the offside trap and cruised into the box, before curling the ball past Ivankov with a perfect shot into the far corner.

But Levski fought back to level, determined to give their all in front of 40,000 of their countrymen.

The home side's first effort on goal eventually came on 25 minutes but Kostadin Vidolov's 20-yard free-kick sailed over the bar, after Steve Finnan fouled Sasha Simonovic.

But that inspired Sofia who worked the ball in from the left and Georgi Ivanov got the chance of a low drive across Chris Kirkland and inside the far post to pull a goal back.

Liverpool responded when Bruno Cheyrou's angled cross beat Ivankov - but also Owen at the far post.

But the Bulgarians were refusing to slip away quietly, and Georgi Chilikov took advantage of some sloppy defending to fire over from the edge of the box.

Levski were needing no extra encouragement to come forward and they did just that five minutes before the break when Simonovic was given the space to smash home the equaliser from the edge of the box.

But Liverpool hit straight back when Dietmar Hamann rose to head home Gerrard's right wing corner - restoring the three-goal aggregate advantage.

Houllier's men almost sprung the offside trap twice at the start of the second half through Gerrard and Owen - but there was plenty of defending to do with Ivanov and Chilikov more than difficult opponents for Sami Hyypia and Stephane Henchoz.

Kirkland twice had to dive at the feet of Ivanov as quick passing again splintered Liverpool's defence, with a concerned Houllier stalking the touchline at this stage.

The visitors then replaced Finnan and Cheyrou with Igor Biscan and Milan Baros - but still the Bulgarians kept going and Kirkland needed to make a fine leaping save to keep out a Simonovic 25-yard effort.

But if there was still any fleeting doubt about the outcome, Hyypia ended it with a low header on 67 minutes from a Gerrard corner for Liverpool's fourth goal of the night

Teams

Levski Sofia Ivankov, Bukarev (Golovskoy 64), Chilikov (Kolev 71), Stanislav Angelov, Stoyanov (Borimirov 62), Temile, Simonovic, Markov, Vidolov, Georgi Ivanov, Topuzakov.

Subs Not Used: Petkov, Biser Ivanov, Stankov, Wagner.

Booked: Topuzakov.

Goals: Georgi Ivanov 27, Simonovic 40.

Liverpool Kirkland, Finnan (Biscan 58), Henchoz, Hyypia, Carragher, Murphy, Gerrard, Hamann, Kewell (Le Tallec 80), Cheyrou (Baros 69), Owen.

Subs Not Used: Dudek, Heskey, Diouf, Traore.

Booked: Henchoz.

Goals: Gerrard 7, Owen 11, Hamann 44, Hyypia 67. Agg (2-6)

Att: 40,281

Ref: Peter Frojdfeldt (Sweden).