Glasgow - Celtic swept St Johnstone aside with three goals inside 26 minutes at McDiarmid Park for a 3-0 win that keeps Neil Lennon's men five points clear of Rangers at the top of the Scottish Premiership.
Rangers were 2-0 winners over Ross County at Ibrox, but victory came at a cost as Jermain Defoe had to be stretchered off with a calf injury.
Celtic made it 30 goals without reply in their last nine games against the Perth Saints as Olivier Ntcham, James Forrest and Leigh Griffiths struck early on.
Ntcham opened the scoring with a powerful header from Forrest's inch-perfect cross.
Greg Taylor, Griffiths and Callum McGregor could all have then added to the lead before the visitors' did double their advantage thanks to a fine finish from Forrest for his 16th goal of the season.
Griffiths's return to form since the winter break continued when he then turned home Taylor's cross for a third goal in four games.
"Some of our attacking play was outstanding," said Lennon.
"It was an all-round great team performance. As a manager, I can't ask for any more."
Rangers, who still have a game in hand over their Glasgow rivals, got back to winning ways after a shock defeat at bottom-of-the-table Hearts on Sunday rocked their title challenge.
Defoe once again started ahead of the Gers top scorer Alfredo Morelos, who is also nursing a calf injury, and broke the deadlock just before half-time.
The 37-year-old then set up Scott Arfield to double Rangers' lead early in the second half before pulling up.
Should Defoe be sidelined for a number of weeks, Rangers boss Steven Gerrard suggested he may have to look at adding more backup to Morelos before the transfer window closes on Friday.
"Hopefully it's not as bad as it looks, but if it's an injury that's more than two or three weeks we've got a problem in that area," said the former Liverpool captain.