Celtic lost defender Christopher Jullien to injury as they prepared for Saturday's Old Firm derby with Scottish Premiership victory over Dundee United.

The Frenchman could not continue after clattering his knee against the post in a second-half goalline clearance.

Ismaila Soro - with his first Celtic goal - and David Turnbull both netted from distance before Odsonne Edouard's lob sealed a sixth straight win.

Celtic head to Ibrox 16 points behind Rangers with three games in hand.

United, who came close through Marc McNulty and Nicky Clark at 2-0 down, remain in fifth place.

A minute's silence was observed before kick-off in memory of legendary United manager Jim McLean, who died on 26 December at the age of 83.

McLean was in charge of the Tannadice club the last time they won at Celtic - 28 years ago - and Micky Mellon boldly shoehorned strikers Lawrence Shankland, Marc McNulty and Nicky Clark into his starting line-up as he attempted to end that long barren run.

There was a big call from Celtic boss Neil Lennon too, with Greek goalkeeper Vasilis Barkas restored in place of Conor Hazard after five games on the bench.

United had coped comfortably with Celtic's heavy pressure until Soro delivered an unlikely opener midway through the first half with a swerving 25-yard drive into the top corner. A moment to savour for the Ivorian, but one to forget for goalkeeper Benjamin Siegrist, whose attempted save was feeble.

Still, United's margin of defeat could have been much heavier had Siegrist not partly redeemed himself with a number of stops.

He made an an instinctive block after Turnbull's outrageous lob teed up Leigh Griffiths for a blast at goal, with Edouard sending the rebound wide.

But another long-range drive doubled the lead as Turnbull drilled home low off the keeper's right-hand post to score for the third game running.

United, anonymous as an attacking force in the first half, almost conjured an instant response after the break as McNulty beat Jullien to Shankland's through ball and fired past Barkas. Jullien raced back to clear off the line, but his impetus took him thudding into the upright and after several minutes' treatment he was replaced by Nir Bitton.

United's positive spell - and Celtic's shakiness at the back - continued when Shankland's cross found Clark 10 yards out but with only the goalkeeper to beat the striker fired horribly wide.

That was as good as it got for the visitors as Celtic regained control. Griffiths and Edouard were both foiled by Siegrist before the strike pair combined to craft a sublime third.

Griffiths' lofted pass split United's defence and Edouard deftly lobbed the keeper as Celtic continued their resurgence before the crucial showdown with Rangers.

Man of the match - David Turnbull

What did we learn?
This was a crucial but costly win for a Celtic side still trying to claw back lost ground in the title race. A fourth consecutive Premiership victory and clean sheet are further evidence of their recovery, but the loss of Jullien is a hammer blow for the trip to Ibrox.

Neil Lennon will at least be consoled by his side's attacking verve, with Turnbull again impressive while the front two of Edouard and Griffiths worked in tandem to torment the visitors.

United's starting line-up was bold, but failed to pay off as Mellon's team were far too passive in a first half, which effectively killed the game as a contest. Standing off and allowing players to shoot cost them the first two goals and their strong start to the second half was let down by wayward finishing.

What did they say?
Celtic manager Neil Lennon: "We played brilliantly and created a lot of really good chances.

"There was great energy and quality. The atmosphere around the place is good and I was really pleased with the substitutes as well, their contribution was excellent."

What's next?
Derby dates for both sides. Celtic face Old Firm rivals Rangers at Ibrox on Saturday (12:30 GMT), while United are in New Firm action away to Aberdeen (15:00 GMT).