Goals from Nikolaj Moller and Panutche Camara sealed Dundee United's spot in the last 16 of the Scottish Cup at Ayr United's expense.

The Swedish striker - introduced as a second-half substitute - turned in Ryan Strain's cross for the game's opening goal before fellow substitute Camara fired home a second in injury time against the Championship visitors.

On a patchy pitch, quality was in short supply, but United had the better of the second half and deserved their victory.

Playing down the slope in the first half, the hosts lacked any real cutting edge.

Ross Graham hooked a shot onto the roof of the Ayr goal, Zac Sapsford was denied by visiting goalkeeper Liam Russell, while Luca Stephenson whipped a shot just wide from the edge of the box.

Ayr's best effort came from striker Anton Dowds, but Dave Richards got down sharply to his left and turned the goal-bound shot round a post.

However, the top-flight outfit improved after the break as Craig Sibbald became increasingly influential.

Amar Fatah tested Russell and Moller put a free header wide as the pressure on Ayr began to build.

And the former Arsenal man made no mistake shortly after when he was picked out by Strain, deflecting the cross from the right beyond Russell.

With time running out, Camara made sure of victory, running onto Kristijan Trapanovski's pass and opening up his body to fire into the back of the net.

After 17 days, United have their first win in January.

Given the nature of the defeats by neighbours Dundee and Celtic in their past two outings, fans would have headed to Tannadice fearing an upset against a side sitting fourth in the Scottish Championship.

And the performance levels again fell below what United fans would expect as simple passes went astray in a forgettable first half.

Things did step up after the break as Sam Cleall-Harding and Sibbald both impressed.

However, there was still a lack of presence up front until Moller's introduction in the 65th minute.

Both he and Camara took their goals well, sparing blushes in a game that looked destined for extra-time.

Scott Brown's Ayr side applied themselves well and went close through Dowds in the first half and Marco Rus in the second, as the Romanian midfielder's shot from range went just wide.

Their focus now returns to the league and their promotion aspirations, as they try to stay in the play-off spots.

Dundee United manager Jim Goodwin tells BBC Scotland: "The cup games are about getting the result and making sure your team is in the hat when the draw comes around.

"We never expected today to be easy or straightforward. Ayr United are a good team, well organised with experienced players.

"Scott Brown has recruited really well and we found it difficult to break them down.

"Second half there was an improvement in the tempo of the game and we deserved to win the game in the end.

"We scored a couple of good goals and Dave Richards had very little to do. The longer the game goes on without the first goal, you can feel the tension, but the players deserve credit for staying calm and finding that all-important first goal."

Jim Goodwin's side return to Premiership action when they host St Mirren next Saturday (15:00 GMT).

Ayr United are away to Partick Thistle in the Championship at the same time.