Giorgios Giakoumakis marked his first start with his maiden goal as Celtic overcame stubborn St Johnstone in the Scottish Premiership to extend their winning run to four games.

Celtic finally made sure of a deserved victory with Josip Juranovic’s penalty.

The hosts stay fourth, a point behind leaders Hearts, Rangers – who face St Mirren on Sunday – and Dundee United.

St Johnstone’s second successive defeat drops last season’s cup double winners to 10th, two points above second-bottom Dundee.

Giakoumakis, a summer arrival from Dutch side VVV Venlo, was unleashed from the start after impressing in the Europa League win over Ferencvaros, his third outing off the bench.

But the 26-year-old and Celtic were superbly marshalled by St Johnstone until Booth’s mistake undid all the visitors’ diligent defending.

Juranovic’s hopeful shot from distance took a looping deflection into the box, where Booth missed his attempted clearance, allowing Anthony Ralston to square for Giakoumakis to volley past Zander Clark.

It brought relief for the hosts and dejection for St Johnstone, who had welcomed back defensive lynchpin Liam Gordon from injury for a first appearance since August.

Bar a Callum McGregor drive stopped by Clark’s outstretched leg, the hosts had struggled to penetrate until Giakoumakis struck.

Kyogo Furushashi, deployed wide right to accommodate the Greek forward in the central striker role, was a peripheral presence but Jota on the opposite flank was Celtic’s liveliest performer.

St Johnstone came out with fresh impetus after the break, Jamie McCart heading over from a corner and Cammy MacPherson slicing high and wide.

Celtic quickly reasserted control, and McGregor had a drive deflected inches wide, but the hosts were restricted to few clear-cut chances until the closing stages.

The clinching goal arrived when Jota and Kyogo combined and the Japan forward – moved centrally after Giakoumakas went off – was caught by Gordon just inside the box. Juranovic sent Clark the wrong way from the penalty spot.

Tom Rogic and McGregor had drives batted away by Clark, either side of a shot off the post by substitute Mikey Johnston, as St Johnstone avoided further damage.

Man of the match – Jota

What did we learn?

Celtic have their key men back and are continuing to build momentum after a chaotic start to Ange Postecoglou’s tenure.

Giakoumakis’ goal will bolster the striker’s confidence as he strives for full fitness, and Croatia defender Juranovic showed his quality after a four-game injury absence.

While Celtic have now won three league matches in a row, St Johnstone have suffered three three defeats and netted just one goal in four.

Davidson’s side will rue the defensive lapses at both goals, but were solid for the most part while lacking threat at the other end.

Gordon’s return to the heart of defence offers hope of a revival, with three of the Perth men’s next four league fixtures at home.

What did they say?

Celtic manager Ange Postecoglou: “It was a game where you know you’re not going to get a lot of space in and around the penalty box and they’re never going to open up.

“It was important we maintained our discipline, moved the ball around and were clinical when the chance came. We didn’t allow St Johnstone to be a threat, and we could have scored a couple more at the end.”

St Johnstone manager Callum Davidson: “Callum Booth misjudged it. It’s not like him. It was a long-range shot and if we deal with that, then we don’t concede.

“I am not blaming Callum. I don’t think Celtic had many chances in the first half but we got punished then the game becomes a little bit harder for us.”

What’s next?

Both sides are in Premiership action against Edinburgh opposition on Wednesday night (19:45 BST), with Celtic away to Hibernian and St Johnstone hosting Hearts.