After a tetchy first half Chris Porter headed the home side into the lead in the 61st minute.

However, former Motherwell striker Scott McDonald levelled barely a minute later with his 30th goal of the season.

With 12 minutes remaining Samaras, on for Jan Vennegoor of Hesselink, bundled home a Barry Robson corner from close range to complete the comeback.

The champions extended their lead over Rangers at the top of the table to eight points but the Ibrox men have four games in hand starting with a trip to Easter Road tomorrow.

But there are no doubts the champions piled the pressure on their city rivals with a win that was based mostly on determination.

The first half, however, was painful viewing. The game simply could not get going due to a series of petty fouls which prevented any flow to the game.

The first real effort on goal came in the 10th minute when Keith Lasley's drive from the edge of the box, after he accepted a Porter pass, was deflected for a corner but Celtic cleared to safety.

The game continued on its ragged way until the 18th minute when Celtic defender Andreas Hinkel took a Paul Hartley pass 30 yards from goal and drove just wide.

Temperatures rose as the crime count mounted and while the home side edged ahead on corners, the Hoops defence handled the set-pieces with some ease.

At the other end, debutant goalkeeper Luke Daniels looked shaky dealing with a Gary Caldwell header following a Shunsuke Nakamura free-kick, the sheer number of Well defenders combining to block McDonald's close-range shot from the keeper's fumble. On the half-hour mark, as the game swung towards Celtic, McDonald forced the ball past Daniels from eight yards out but was ruled offside.

In the 35th minute Fir Park full-back Brian McLean rose to head a Lasley corner over the bar with Artur Boruc in the Celtic goal remaining untested.

But the Poland international was called into action two minutes later when Marc Fitzpatrick ran on to a Darren Lee cross and fired in a right-footed shot from 16 yards, but even then Boruc looked comfortable enough.

The pock-marked Fir Park pitch did not lend itself to pretty football but the 9,158 fans were still looking for a marked improvement in the second half which began, unsurprisingly, with a couple of free-kicks within the first minute.

However, the match stubbornly refused to improve. Possession changed hands within seconds of most players taking the ball and there was always the hint that the increasingly grumpy game could boil over.

But in the 61st minute the home side took the lead with their first chance of the game.

Celtic never really cleared their lines following a misunderstanding between Boruc and Lee Naylor which led to a throw-in on the right.

When McLean's whipped cross came into the Parkhead penalty area, Porter nipped in ahead of Bobo Balde to head past Boruc high into the net from around six yards out.

But a minute later Celtic were level when McDonald scored his 30th of the season, taking advantage of slackness in the Well penalty area to head Nakamura's cross past Daniels from close range.

Samaras and Scott Brown replaced Vennegoor of Hesselink and Nakamura soon after as the visitors geared up to go for the winner.

And in the 79th minute it was the Greek striker - on loan from Manchester City - who gave Celtic the lead with their first corner of the match.

Robson's cross somehow found its way through a packed penalty area and Samaras bundled the ball over the line from around two yards out with his head.

In the final minute Boruc got his hand on a Porter header to concede a corner but the champions saw out three minutes of added time to keep their title ambitions alive.