Match ends, Celtic 2, St. Johnstone 0.
Celtic 2-0 St Johnstone: Leaders six points clear after McGregor & Christie goals
Celtic moved six points clear at the top of the Scottish Premiership after two goals in two second-half minutes broke St Johnstone's resistance.
Callum McGregor fired low from outside the box eight minutes after the break, then Ryan Christie curled in a second.
Scott Sinclair's header had been well saved by Zander Clark as Brendan Rodgers' side dominated.
St Johnstone offered little in attack as they suffered successive away losses for the first time since September.
Tommy Wright's team, who were beaten at Hearts on Saturday, remain sixth - five points clear of Hibernian.
And the Perth outfit host Rodgers' men on Sunday before returning to Celtic Park in the Scottish Cup on 10 February.
Visitors resistance eventually falters
Celtic took the points, but only after a stubborn and robust defensive effort in the first 50 minutes by St Johnstone.
Jason Kerr - who on Tuesday signed a contract extension until 2022 - and Joe Shaughnessy were a composed and diligent central defensive pairing and frustrated the Premiership leaders.
One particular highlight from Kerr was a clever backward header just before half-time to defuse an awkward situation caused by Mikael Lustig's cross.
Clark also deserves credit, because the visiting goalkeeper sprang into action with a wonderful diving save to claw out Sinclair's header on the half hour.
He went on to pull off another great save from McGregor, but Celtic had seized control by then.
Just after the break both McGregor and Christie were teed up by Lustig, who occupies the right-back berth that Celtic are so keen to strengthen.
Manager Rodgers said pre-match that there was nothing to report in the speculated interest in Borussia Dortmund's Jeremy Toljan.
Christie's looping curler into the top left corner was definitely the more pleasing of the two goals.
McGregor strike's was low into the same corner, with Clark perhaps unsighted by a ruck of defenders.
Celtic had the luxury of bringing Odsonne Edouard, Timothy Weah and Nir Bitton on as substitutes, with strikers Edouard and Weah going very close to making it three for the hosts.
Celtic send out 'ominous' warning - analysis
In this extremely competitive season, Celtic have used their game in hand to establish a more commanding advantage - something that seemed unlikely pre-Christmas when the league lead was being exchanged almost on a weekly basis.
Celtic's dominance and eventual attacking prowess is an ominous warning to others in the top-four positions, who have to muster the season-long title-challenging stamina to reel Rodgers' men back in.
If captain Scott Brown does finally commit his future to Celtic in the next few days, it might offer the club that one extra spur to complete the job in the league this season.
St Johnstone were always in for a difficult night and their initially resolute performance was worn down. Wright will look to Sunday's meeting with Celtic on their own McDiarmid Park patch as a better chance to show what they are capable of against the leaders.
Celtic were 'very calm' - reaction
Celtic manager Brendan Rodgers: "The first 20, we didn't play quick enough but then we started to get into better areas. Second half, we were very, very good and scored two wonderful goals.
"We didn't give up so much at the back, we were very calm. We scored two wonderful goals, the keeper makes another couple of saves and we should have a penalty as well."
St Johnstone manager Tommy Wright: "I can't fault my players for their effort, their energy that they showed and they're up against a team just full of quality.
"Sometimes you've just got to take your hat off to them and say that you're beaten by the better team."
- 17ChristieBooked at 32minsSubstituted forBittonat 81'minutes
- 11SinclairSubstituted forWeahat 74'minutes
- 25BurkeSubstituted forEdouardat 68'minutes
- 4AlstonSubstituted forKennedyat 81'minutes
- 8DavidsonBooked at 70mins
- 11SwansonSubstituted forCallachanat 65'minutes
- 17O'HalloranSubstituted forWattat 65'minutes
- Greg Aitken
- Shots on Target
Second Half ends, Celtic 2, St. Johnstone 0.
Foul by James Forrest (Celtic).
Scott Tanser (St. Johnstone) wins a free kick on the right wing.
Foul by Timothy Weah (Celtic).
David Wotherspoon (St. Johnstone) wins a free kick on the right wing.
Corner, Celtic. Conceded by Richard Foster.
Corner, Celtic. Conceded by Scott Tanser.
Attempt saved. James Forrest (Celtic) header from the centre of the box is saved in the centre of the goal.
Attempt missed. James Forrest (Celtic) right footed shot from the right side of the box is too high.
Corner, Celtic. Conceded by Joe Shaughnessy.
Foul by Kristoffer Ajer (Celtic).
Tony Watt (St. Johnstone) wins a free kick in the defensive half.
Attempt saved. Callum McGregor (Celtic) left footed shot from outside the box is saved in the bottom left corner.
Substitution, Celtic. Nir Bitton replaces Ryan Christie.
Substitution, St. Johnstone. Matthew Kennedy replaces Blair Alston.
Attempt saved. Odsonne Edouard (Celtic) right footed shot from the left side of the six yard box is saved in the bottom left corner.
Corner, Celtic. Conceded by Zander Clark.
Attempt saved. Timothy Weah (Celtic) right footed shot from outside the box is saved in the bottom left corner.
Substitution, Celtic. Timothy Weah replaces Scott Sinclair.
Attempt saved. Scott Sinclair (Celtic) right footed shot from outside the box is saved in the top left corner.
Scott Sinclair (Celtic) wins a free kick in the attacking half.
Foul by Liam Craig (St. Johnstone).
Mikael Lustig (Celtic) wins a free kick in the defensive half.
Murray Davidson (St. Johnstone) is shown the yellow card for a bad foul.
Foul by Murray Davidson (St. Johnstone).
Substitution, Celtic. Odsonne Edouard replaces Oliver Burke.
Attempt blocked. David Wotherspoon (St. Johnstone) right footed shot from the left side of the box is blocked.
Corner, St. Johnstone. Conceded by Scott Brown.
Foul by Scott Brown (Celtic).
Ross Callachan (St. Johnstone) wins a free kick in the attacking half.
Substitution, St. Johnstone. Ross Callachan replaces Danny Swanson.
Substitution, St. Johnstone. Tony Watt replaces Michael O'Halloran.
Attempt missed. Ryan Christie (Celtic) right footed shot from outside the box misses to the right.
Attempt missed. Scott Brown (Celtic) right footed shot from outside the box is high and wide to the right.
Attempt blocked. James Forrest (Celtic) right footed shot from outside the box is blocked.
Attempt missed. Ryan Christie (Celtic) header from the centre of the box is close, but misses to the left.
Foul by Emilio Izaguirre (Celtic).
Blair Alston (St. Johnstone) wins a free kick in the defensive half.
Goal! Celtic 2, St. Johnstone 0. Ryan Christie (Celtic) left footed shot from the right side of the box to the top left corner. Assisted by Mikael Lustig.