The club said at first that he had quit Parkhead without kicking a ball, but now say he is travelling to his native country.

It follows apparently false reports that the striker had checked into a clinic.

Viduka's agent has denied that he has any mental problems and the player says he simply needs a rest.

The Australian was first linked with a move from Croatia Zagreb in August, but due to work permit problems the move was held up and Viduka only started training in Glasgow on Thursday.

He did not train again on Friday, and on Saturday appeared to have left the club, with Celtic saying he was suffering from depression.

A first official statement said he "greatly regretted being unable to join the club, but that the way he felt he could not play football for any club".

This brought an angry response from Viduka's Australian agent who insisted the player was not depressed and had not left.

'False' clinic claim

The story then appeared to change overnight, with a Press Association report quoting a statement from the club as saying Viduka had checked into an unknown Aberdeen clinic.

But on Sunday the club issued an official statement confirming that Viduka had returned to Australia.

"Recent reports regarding Celtic reaching an agreement for Marko Viduka to attend a clinic are false," it said.

"A statement indicating this was not issued by Celtic.

"It is Celtic's understanding that the player has left the country. Further comment will be made today following Celtic's match against Hearts."

The mystery has overshadowed the Bhoys' preparations for that game, but the striker has urged Celtic fans to be patient and await his recovery.

I'll be back

He issued his own statement through his agents International Management Group (IMG).

It said: "It was only after I arrived in Glasgow last week that I started to realise how much I had been affected by events in Zagreb over the last few months where I had been under enormous personal pressure.

"I arrived ready and wanting to play, but it finally became apparent that having thought a change would be as good as a rest, I realised I actually badly needed a rest.

"It would have been relatively easy for me to cover this up for a few weeks, but that would not have been fair on the club, the fans or my family.

"I just hope everyone realises this is not easy for me and appreciates my honesty.

"I realise this is causing great embarrassment and disappointment at the club who have been very supportive and understanding. I would just ask everyone to be patient while I get back to full fitness as soon as possible."

Bernie Mandic from IMG, who represented the Australian international during his transfer, added: "There's no personal problems with him; there's no girl problems, but it appears everything is on hold at the moment. He is a little confused as to why they put out that statement."