Martin O'Neill marked his first game back in charge by returning Celtic to second place in the Scottish Premiership - and within three points of leaders Hearts - with a comfortable victory over struggling Dundee United.

After last weekend's bruising Old Firm defeat, one which spelled the end of Wilfried Nancy's 33-day reign, O'Neill returned to lift Celtic's spirits.

Celtic were all over a hugely defensive United in the first half and the breakthrough came from Yang Hyun-jun, whose low drilled strike deflected off a defender and fizzed into the back of the net.

Arne Engels doubled the hosts' advantage five minutes later when he fired home Kieran Tierney's cross with a one-touch finish from close range.

United, when they did manage to escape their own half, created a few decent opportunities.

Owen Stirton had a chance to level at 1-0 when he robbed the ball from Auston Trusty, but the teenage striker took too long over the strike and allowed Liam Scales to track back and clear the danger.

The second half was more of the same from Celtic and United, having adopted a more progressive approach, were repeatedly picked open.

Substitute Benjamin Nygren added a third from close range before Daizen Maeda slotted in the fourth after Dave Richards failed to hold Sebastian Tounekti's strike.

The result leaves United seventh - level on points with Aberdeen, but now five behind Falkirk having played a game more - while Celtic leapfrog Rangers before Danny Rohl's side visit Pittodrie on Sunday.

The feelgood factor is well and truly back at Celtic Park.

After Nancy was sacked earlier this week, the Celtic support needed something to cheer about. They got it when O'Neill was confirmed as interim manager again.

While there were perhaps questions about whether the 73-year-old could replicate the form of his previous interim spell - during which he won all of his Premiership fixtures and seven out of eight games overall - any doubt was cast aside here.

It was as emphatic a victory as you can get - a clean sheet, four goals, 22 shots (eight on target), 78% possession, and most importantly three points.

Celtic looked like they were playing with a confidence and self-assuredness that was sorely lacking during Nancy's tenure.

They were solid at the back - Liam Scales in particular looked back to his best - and looked dangerous in attack, and were unlucky not to have had a few more goals.

For United and Jim Goodwin the worries continue.

They failed to attempt a single shot on target, and have now gone 51 games since last winning at Parkhead in December 1992.

This was the first time since facing Aberdeen in October 2024 that they have not managed an attempt on target in the Premiership. And their three shots is the lowest in a league game this season.

Their 22% share of possession speaks volumes about the lack of control they had.

The table is starting to look a little ominous for Goodwin. They stay level on points with Aberdeen and only three above Dundee - both of whom play on Sunday - and drop five behind Falkirk having played a game more.

Celtic interim manager Martin O'Neill: "It was delightful, we played really well in the game and in the end we won quite convincingly.

"You still have to score the first goal in the game, Yang takes it magnificently and we get up and running but the performance was really good.

"Some of the players are just back to a bit of form that I know they can produce and that was the lovely thing about today's performance. Overall I thought we were excellent."

Dundee United boss Jim Goodwin: "They're playing a formation and a system that the players are familiar with, and one that suits the squad they've got.

"When you come here you know you're going to be starved of possession at times and you have to really show a bit of resilience in and around your penalty area and I think today there's lots of areas within the goals we've conceded we could've done a lot better."

Celtic face Falkirk on Wednesday (19:45 GMT) - the first of four consecutive away games.

United, by contrast, play their next three fixtures at Tannadice, with Ayr United their next opponents on Saturday (15:00) in the Scottish Cup fourth round.