Riga is in dispute with his Spanish club after they failed to pay his wages for nine months.
Must have a go: Mustapha Riga of Levante (right) takes on Real Madrid's Miguel Torres
He has penned a two-year deal with Bolton on the proviso he can join them as a free transfer.
Levante want a fee of £500,000 and the matter is expected to end up before a judge before his future is decided.
Meanwhile, West Brom are ready to make an improved £2m bid for Bolton defender Abdoulaye Meite.
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London gets ready for the Diamond Jubilee - in pictures
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EXCLUSIVE: I won't play with Joey Barton, says Adel Taarabt
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Diamond Jubilee: Boat by boat, here is where to watch the Queen's Thames flotilla - VIDEO
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Duchess of Cambridge is pretty in pink at her first Buckingham Palace garden party
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News pictures of the day
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‘We will form a human barricade to keep missiles off our homes’
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Regent’s Park rapist: Teenage jogger assaulted by stranger in terrifying 7am attack -
Major Coalition u-turn as George Osborne scraps ANOTHER tax plan
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Horror on the 5.53! Commuter dragged 200 feet after getting hand trapped on train -
Hunt-ed: Labour pile on pressure for Culture Secretary
Why I think doctors are right to strike 
Family pay tribute to the London man who gave his life to save a five-year-old girl from drowning 
Eton schoolboys fly Games flag on Everest 
Shrimpy's - review 
The O2
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Playing a game-changing role during the Games
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Win a Silverstone track day with Zantac 75
Feel the burn of a different kind - 20 Silverstone motoring experiences to be won
Celebrate with MARTINI®
This weekend toast one royal with another and make your Jubilee sparkle with a MARTINI Royale.
Rock star
Happy anniversary
Victoria Coren
Summer party
Diamond Jubilee
Glamour Awards
Garden party
First review
Fair-weather goths
Dog save the Queen
