Frank Lampard and John Terry were on target for the Blues, but the home side, inspired by one-time Manchester United reserve Erik Nevland, got the four goals they required to progress.

One of Claudio Ranieri's first acts as Chelsea boss was to oversee a humbling exit at the hands of Swiss minnows St Gallen two years ago, and last season Israelis Hapoel Tel Aviv proved that lightning does strike twice.

A late away goal from Viking substitute Ben Wright at Stamford Bridge had left Chelsea nerves on a knife-edge coming into the second leg, and Blues fans knew they were in for a nail-biting night when their hosts took the lead on nine minutes.

Carlo Cudicini and John Terry got in each other's way from a right-wing corner, Graeme Le Saux cleared from under his own bar, and when Morten Berre forced the loose ball goalwards, it crossed the line before William Gallas could hack clear.

That would have been enough to send Viking through, and their chances improved still further as the outstanding Nevland laid on a second for Peter Kopteff, who finished high past Cudicini from 15 yards.

Ranieri cut a worried and wet figure on the touchline, but his half-time team-talk was made a mite easier as the Blues pulled one back in injury-time.

Lampard had gambled to get beyond the strikers on several occasions with little success, but when Jimmy Floyd Hasselbaink failed to control an incisive Gianfranco Zola pass, the England midfielder burst through to slot home from around the penalty spot.

With Jesper Gronkjaer a constant menace on the Chelsea right, it looked a matter of time before Chelsea added to their tally after the interval, but the next goal was Viking's.

Hasselbaink showed a striker's touch in trying to clear a Norwegian corner, and when the loose ball was headed back in, half the Chelsea defence charged out and half stayed put as Nevland nodded his first of the night.

But Viking had no sooner smelt the third round than the prospect was snatched away from them, John Terry marking his return to first-team action with a simple back-post header from Graeme Le Saux's wicked in swinging corner.

Job done, it seemed, as the urgency disappeared from a tiring Viking side and the dangerous Kopteff was forced off by aching limbs.