A quick-fire headed double from Jan Vennegoor Hesselink put Celtic into the lead at the Caledonian Stadium and they looked extremely comfortable until John Rankin scored a penalty four minutes prior to the interval which filled the Highlanders with confidence.

A match that Strachan branded as "bizarre" then continued to thrill as Vennegoor of Hesselink hit the post, before Inverness surged ahead of the visitors thanks to David Proctor's 57th-minute header and Don Cowie's prodded finish.

Caley Thistle were soon reduced to 10 men when Proctor was sent off for denying Scott McDonald a clear goalscoring opportunity and that gave Celtic 22 minutes to try and benefit from their numerical advantage.

But Inverness withstood Celtic's late charge, leaving Strachan stunned at the outcome.

He said: "I am in a state of shock and I thought it was the most bizarre game of football.

"After 40 minutes I was asking myself 'are you sure we are at Inverness?' because normally it is like a cup tie here and we were 2-0 up, while it could have been three or four.

"Then they got a penalty and whether it should have been given or not, I am not sure."

It was Steven Pressley who conceded the spot-kick as he desperately tried to prevent Marius Niculae from getting a shot in on goal.

But as the Romanian still managed to make a firm connection with the ball despite the Celtic defender's attentions, Strachan questioned whether the penalty should have been awarded by referee Alan Freeland.

He said: "The ball was played on, they had an attempt at goal and then the referee gave a penalty.

"I thought playing on gave you an opportunity to use the advantage and if you didn't use that advantage then it can't be pulled back."

The key stage in the contest then took place in the four minutes immediately following Proctor's equaliser.

McDonald saw a goal chalked off for offside and soon afterwards Cowie pounced to find the back of the net when Stephen McManus failed to cut out a long ball from Richard Hastings.

Strachan was adamant McDonald's goal should have stood, although the Celtic boss conceded his players must do far better at the back as the Parkhead club conceded away from home for the 34th consecutive game.

He said: "Scott McDonald had a goal ruled out which everyone could see was not offside so circumstances went against us. But we are not getting away from the problem that we have to defend far better."

Despite Celtic's defensive deficiencies, Strachan refused to comment on speculation linking Seville full-back Andreas Hinkel with a move to Glasgow, saying: "I am not talking about anything bar the game just now."

Inverness player-manager Craig Brewster paid tribute to the spirit of his team but downplayed the significance of the victory, maintaining it was "just another three points."

This was the first occasion Inverness had beaten Celtic in the top flight - although the Highlanders do hold two stunning Scottish Cup victories over the Hoops to their name.

Brewster added: "It was a big win for us, especially under the circumstance of going two goals down.

"You have to give the players a lot of credit for coming back and I thought they were exceptional in the second-half.

"It is nice to have beaten Celtic given the quality of their team, but at the end of the day it is still only three points."