David Connolly took another small step towards repaying his hefty transfer fee with a second-half winner for resurgent Sunderland against rivals Luton.

The Republic of Ireland striker, a £1.4million deadline-day signing from Wigan in August, netted only his second goal of the season in the 53rd minute to extend the Black Cats' unbeaten run to six games.

Connolly has struggled with injuries since his arrival at the Stadium of Light but he showed he has lost none of his predatory qualities with the all-important winning goal.

After an inconsistent start to his managerial career at Sunderland, Roy Keane is now conjuring the kind of consistency required from his players to make a serious bid for a play-off spot.

However, they were forced to endure an early scare as Luton striker Dean Morgan opened the scoring in the fifth minute. Morgan displayed unerring accuracy as he collected possession and hit a 20-yard shot into the bottom corner of the net.

Sunderland's response was impressive and two minutes later midfielder Graham Kavanagh hit a 30-yard shot just wide.

A breathless opening then almost saw the visitors double their advantage as Ahmet Brkovic's header forced Marton Fulop into a smart stop.

In the ninth minute, though, Sunderland were level as striker Daryl Murphy was on hand to hit a powerful left-footed shot into the top corner from 12 yards.

It was the Waterford man’s third goal in as many games and his fifth of the season but Luton continued to probe and created several noteworthy goalscoring opportunities.

In the 11th minute, Morgan saw his 12-yard shot blocked by Stanislav Varga and moments later Rowan Vine saw his low drive flash just wide of the far post.

Brkovic came close again on the half-hour mark which forced Fulop into action but Murphy was soon back in the thick of the action.

He hit a vicious shot from 20 yards which forced Dean Kiely to parry and then strike partner Stephen Elliott produced a similar effort which again forced Kiely into action.

Three minutes before the break Luton threatened once more when Vine came within inches of scoring with a well-struck 18-yard shot.

A flurry of activity shortly before the break could and should have led to further goals.

Elliott saw his shot blocked by David Bell and then Kiely produced another impressive save to deny Connolly from close range.

In first-half injury-time, a superb inswinging corner was greeted by a firm header from Steven Caldwell, but his header lacked precision and flew over the crossbar.

Seven minutes before the break, though, Sunderland were ahead as Connolly fired into the bottom corner from 20 yards.

But Luton continued to attack and Carlos Edwards narrowly missed with a long-range strike in the 66th minute and then Brkovic failed to hit the target after connecting with Bell's corner at the near post.

However, Sunderland held on to take another significant step towards the play-off places.