TOKYO (Kyodo) -- Kyogo Furuhashi struck a brace and Daizen Maeda added a goal off the bench as Scottish Premiership leaders Celtic ended the calendar year in dominant fashion Sunday with a 4-0 victory at home to St. Johnstone.

The result extended Celtic's unbeaten run to 18 Scottish top-flight football games this season and moved them 14 points clear of closest rivals Rangers ahead of their clash in the Old Firm derby Thursday at Ibrox Park.

The defending champions took a 1-0 lead into the break at Celtic Park on Nicolas Kuehn's 30th-minute opener, assisted by Japan midfielder Reo Hatate.

Fellow Samurai Blue squad member Furuhashi notched his first goal of the game, and Celtic's 50th of the league campaign, with a header from close range in the 59th minute.

He bagged his brace five minutes later off a ball whipped in from the right by Belgian midfielder Arne Engels.

"I think (it was a) very good performance. I'm just happy to help the team," said Furuhashi, who credited Engels for the second goal.

Japan forward Maeda, rested from his normal starting role by manager Brendan Rodgers, came on as a substitute and completed the scoring with a clinical finish off a through ball from Paulo Bernardo in the 73rd minute.