New signing Kyogo Furuhashi scored in his first start as former Socceroos boss Ange Postecoglou finally got his Celtic reign up and running in the Czech Republic.

Japan international Furuhashi scored Celtic's second goal in a 4-2 first-leg victory over Jablonec in their Europa League qualifier on Thursday.

Another summer signing, Liel Abada, had opened the scoring early on and both James Forrest and Ryan Christie restored Celtic's two-goal cushion in the second half after their defensive frailties reared their head again.

Postecoglou's first win in four matches in charge of Celtic put his team on course to face AZ Alkmaar in the playoffs.

Yet the Australian was still not overly impressed by much of what he saw in his maiden win.

"The performance was okay. We started really well, the first half hour was excellent, and controlled the game. I felt we lost our way a little bit after that especially second half, and lost control of the game," said Postecoglou.

"Second half, we were doing OK but didn't really control the game the way we should have to make sure we won the game more comfortably.

"The result is obviously a positive one. I think it's important, particularly for the players, who have been working hard. Every competitive game we have had an opportunity to win, which we haven't done.

"It's a reward for the players and hopefully gives them confidence and belief moving forward.

"A whole range of aspects left the game really open. We still had chances at the same time but it's not the way I want us to play."

Postecoglou handed goalkeeper Joe Hart a debut 24 hours after the goalkeeper completed his move from Tottenham, while Furuhashi was preferred to Odsonne Edouard up front.

Celtic took the lead after 12 minutes. Forrest played the ball inside to Greg Taylor and the left-back's low cross was swept home by Abada after his initial effort was blocked.

Celtic went two up inside 16 minutes, Furuhashi setting himself up with his first touch and dinking the ball over the goalkeeper.

The hosts responded inside 60 seconds, Vaclav Pilar running on to a lofted through ball and knocking the ball past a static Hart.

Forrest finished high into the net before Celtic's defence were caught out by a ball down the left to Tomas Malinsky. The Jablonec player chipped Hart, who got a hand to it, but the ball came off the post and hit Bitton and went in.

The goal gave the hosts hope but Forrest crossed for substitute Christie to steer home a diving header in the 90th minute.

Meanwhile, Socceroos striker Martin Boyle scored for Hibernian in their 1-1 draw with Rijeka in the first leg of their Europa Conference League third qualifier at Easter Road.

Ghanaian attacker Prince Ampem headed the visitors ahead on the hour mark but Socceroos striker Boyle levelled six minutes later with a close-range finish.