Song joined the Catalans two years ago from Arsenal for a fee of �15 million ($25 milllion, 19 million euros), but has since struggled to hold down a regular place in the first team.

The 26-year-old made 65 appearances in total for Barca scoring just the one goal.

Song was paraded in front of the West Ham fans ahead of their Premier League match at home to Southampton on Saturday but hadn't been registered in time to play.