Barton was handed a free transfer on Monday after the club finally lost patience with the player's Twitter rants against the Magpies hierarchy.
But he was back on Tuesday morning and Tweeted: 'Just off to training... getting close to start now.'
Before: 'Made to train alone today, how predictable...'
This charming man: Joey Barton gives the thumbs up arriving at training
Tottenham are favourites to sign the former Manchester City man but Aston Villa, Stoke, Blackburn and Fulham are also interested.
And Bolton boss Owen Coyle said: 'He's a very talented player. We know that. There's no doubt Joey will have very attractive offers because he's a talented player.'
Barton, who often tweets lyrics from The Smiths as well as updates on football matters, used his Twitter account to criticise Mike Ashley's regime and the Toon owner, manager Alan Pardew and managing director Derek Llambias ripped up his contract.
Barton, who on Sunday evening had hinted at unrest among Newcastle players following the 3-2 defeat at Leeds, announced the following day via Twitter that he would be making a statement about his future at 4pm.
But Newcastle stole his thunder and put out a two-paragraph press release 23 minutes before his deadline, stating he had been placed on the transfer list and 'advised he can leave the club on a free transfer'.
Bigmouth strikes again: Barton is a big fan of Twitter
Barton's 140,000-plus followers then had to wait almost an hour before he posted three tweets.
He said: 'Somewhere in those high echelons of NUFC, they have decided, I am persona non grata.'
Then: 'I am on a free but the honour of wearing those B+W stripes, surpasses that.'
Finally: 'One day the board might realise what the shirt signifies HONOUR and PRIDE. Thanks for your continued support.'
His agent Willie McKay claimed Barton would have been happy to take a pay cut and branded the decision to release him 'suicidal'.
That joke isn't funny anymore: Newcastle manager Alan Pardew has finally had enough
McKay said: 'I was totally surprised when they never offered him a contract. I think it's a wee bit suicidal by Newcastle because how would you let your player of the year leave on a free transfer, approaching his prime.
'He had a great season and, for me, was pivotal for the club getting ?35million for Andy Carroll because he passed every ball to Carroll for every goal.
'Derek Llambias and Mike Ashley stood by Joey when he was under real pressure, so I'm not going to slag off Newcastle's board, but I think they have made a mistake. He was going to take a drop in wages to sign a new contract.
'A couple of top clubs have been in contact already. There won't be a problem finding Joey a home. I think he is capable of playing Champions League. He's a very good player.'
The Liverpool-born midfielder, who joined Newcastle from Manchester City for ?5.8milliion four years ago, was on an? ?80,000-a-week contract.
After the defeat at Elland Road, where he had expected to captain the side but did not, Barton indicated full support for Jose Enrique, who was fined last week by the club after he used his Twitter account to hit out at Newcastle's lack of ambition and summer transfer policy.
Enrique was expected to play at Leeds but failed to appear.
I started something I couldn't finish: Barton won't see out his contract
Barton said: 'If only we as players could tell the fans exactly how it is, without them above fining us lots of money. There will be a time and a place.'
He added: 'If it wouldn't affect team morale and cause unrest within the dressing room, am certain Jose's comments would be the tip of the iceberg.
'And again it would be left to those magnificent fans to pick up the remnants of their once great football club.'
Pardew, who is expected at Gateshead on Tuesday night for a? reserve-team run-out, could face a backlash from supporters upset by the sale of Kevin Nolan to West Ham and the failure to re-invest the Carroll cash on new players.
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Source: Daily Mail
Source: Daily Mail