Striker Georgios Samaras scored twice as Celtic put the pressure on rivals Rangers with a 2-0 victory in the Old Firm derby at Ibrox.
Neil Lennon's side move four points clear at the top of the SPL, although Rangers have two games in hand over their fierce rivals.
Celtic's new signing Freddie Ljungberg failed to make the squad after picking up a virus as the teams observed a minute's silence to mark the 40th anniversary of the Ibrox Disaster.
After a goalless first half, Samaras opened the scoring shortly after the hour mark, chasing down Joe Ledley's long through-ball to slide the ball past the advancing Allan McGregor.
And the Greek doubled the Hoops' lead from the spot after he was brought down by Madjid Bougherra in the penalty area, firing a low strike past a helpless McGregor.
He was denied his hat-trick in the dying minutes as McGregor produced a finger-tip save to steer the ball roud the post, but Samaras' efforts were enough as Celtic returned to Parkhead with the points.
Inverness finally lost their long unbeaten league away record stretching back more than a year as substitute Collin Samuel fired St Johnstone to a dramatic late 1-0 victory in Perth.
The Highland club had been unbeaten on their travels in the Premier League all season and had last lost away from home in the league as a First Division club on November 28, 2009, to Partick.
St Johnstone had previously managed a meagre haul of just four goals at McDiarmid Park all season in the top flight and it looked as if Inverness would hold out for a hard-earned goalless draw with goalkeeper Ryan Esson impressing.
With five minutes remaining, however, Samuel, who had already spurned a clear opening to score, netted from close range after a Dave Mackay effort had been hacked off the line.