Tennent's Scottish Cup holders Celtic survived a blackout, a downpour and the threat from Kilmarnock's young chargers to power into the fifth round with victory at Rugby Park.

In a night of high drama the game only just went ahead following three pitch inspections by Hugh Dallas after heavy rain and then a power-cut delayed the kick-off by 45 minutes.

It also took Celtic some time to flicker into life after half-time - but an own goal from Garry Hay and Henrik Larsson strike kept their burning Treble ambitions alive.

Martin O'Neill's men now face another all-Premier League tie at Aberdeen in the last eight - but tonight's action did not look possible after the worrying events before kick-off.

The first-half failed to live up to the excitement of the pre-match build up and there was little goalmouth action in a scrappy opening to the game.

Celtic, however, began to settle down and Jackie McNamara sent Larsson through on goal after 10 minutes only to be pulled back by the linesman for moving just off-side.

The Kilmarnock fans soon found their voices as Bobo Balde, who came under fire from the Hearts camp after a tackle in midweek, put in two thundering challenges on former Celt Tommy Johnson.

Stephen Murray then took some retribution by clattering the Frenchman, but referee Dallas took no action against them or Neil Lennon for a late tackle on Garry Hay.

The opening of the game was so uninspiring that it took 20 minutes for the game to come to life when Stilian Petrov squandered a glorious opportunity to put Celtic ahead.

The lively John Hartson played the ball back to Larsson, who picked out the unmarked Bulgarian in the centre, but he powered his header just over the bar from just six yards.

The visitors took confidence from that and enjoyed their best spell of the first-half with Kilmarnock's defence looking nervous.

Thompson found Larsson and the Swede swung the ball in high. Keeper Gordon Marshall failed to collect under the challenge of Hartson, but fortunately the ball bounced wide.

The Kilmarnock keeper was also relieved in the 25th minute when Thompson's corner hit Balde and fell kindly for him to claim.

The heavens opened again which coincided in Kilmarnock's best spell of the game, but Ally Mitchell's low 25-yard drive was comfortably saved by Robert Douglas in the 37th minute.

The home midfielder again tried his luck minutes later after being teed up by Johnson, but this time he blazed his right-foot effort well over the Celtic crossbar from beyond 25 yards.

Celtic though needed a vital clearance from Alan Thompson in the 43rd minute to save his side a late blow before the break as he cleared Johnson's header from Murray's corner off the line.

The visitors, however, got their noses in front just six minutes after the restart.

Thompson swung in a free-kick to the near post where Larsson was lurking, but it was Hay's outstretched boot which made contact and sent the ball into his own net.

Kilmarnock looked shellshocked and the visitors almost doubled their lead two minutes later.

McNamara swung in a great cross, but Petrov just could not make up enough ground and was stretching as he headed over the bar.

Larsson tried to kill off the tie in the 57th minute as he outstripped Frederic Dindeleux for pace, but he dragged his shot into the side-netting from a wide angle.

The Swede, however, did double Celtic's lead in the 63rd minute when Thompson chipped the ball over the Kilmarnock defence and he took one touch before dispatching the ball low past Marshall.

That was his 24th goal of the season and followed his match-winning double in midweek to suggest that his confidence was back after giving Hartson penalty duties in the recent win here.

Kevin McGowne whistled a long-range free-kick past the post before Thompson's chip glided just over the bar.

Larsson could have capped off the win with his second late on as he headed substitute Bobby Petta's free-kick straight at Marshall.

Kilmarnock could have got a consolation in the dying seconds after Douglas had saved Johnson's shot, but Kris Boyd blazed wide from the rebound with the keeper grounded.

Celtic now go to Pittodrie next month - but the holders will not have any fears after coming through today's drama.

Teams

Kilmarnock: Marshall, Fowler, McGowne, Dindeleux, Hay, Canero, Mahood, Mitchell, Murray (Dargo 71), Johnson, McLaren (Boyd 71).

Subs Not Used: Meldrum, Hessey, McDonald.

Celtic: Douglas, Mjallby, Balde, Valgaeren, McNamara, Lennon, Lambert (Sylla 81), Petrov, Thompson (Petta 87), Larsson, Hartson.

Subs Not Used: Gould, Boyd, Moravcik.

Goals: Hay 53 og, Larsson 63.

Att: 11,269

Ref: H Dallas (Scotland).