Adnan, who was the equal runner-up for the 2009 Asian Player of the Year award behind Japan's Yasuhito Endo, was recently released by Qatari club Al Khor.

The 28-year-old, who has 79 international caps to his name, was one of three Bahraini players who were detained following anti-government protests in Manama in April.

Roar coach Ange Postecoglou is understood to be keen to bolster his defence, following the departure of Milan Susak to Indonesia, as well as Luke DeVere to Korea in January.

"He came to the club looking for a change and we're happy to give him a chance," Postecoglou told The Courier Mail.

The lanky Adnan is known as a danger from set-pieces and has scored 13 international goals for Bahrain, although he infamously missed a penalty in their 2010 World Cup inter-continental play-off defeat to New Zealand.

Adnan was not part of the Bahrain squad which faced Australia at the 2011 Asian Cup, but did play against the Socceroos in a World Cup qualifier in Manama in November 2008.