Brutal terror group Islamic State (Isis) passed a strict law forbidding anyone in its territory from watching last weekend's El Clasico football match.

The fundamentalist group enforced the ban with a punishment of 80 lashes for anyone caught watching the clash in Spain between Real Madrid and Barcelona.

The Sun reported a source in the region spanning Syria and Iraq explaining that the fanatics despise the world's most famous match because it a product of the "decadent West".

"IS prohibits watching and playing any sport, particularly football as it seen as a product of the decadent West," said a member of the opposition figure from the Kurdish Democratic Party.

Last month, IS murdered 13 teenage boys for enjoying a Asian Cup football match on television. They were killed by firing squad in the Iraqi city of Mosul and their bodies then left in the street in a warning to others, activists said.

IS has declared an Islamic caliphate in the swathes of territory across Iraq and Syria which have fallen in to its hands. An unlikely alliance of regional powers backed by the US is resisting the terror group's advance and trying to reverse its gains.

The Iraqi city of Tikrit has been targeted in US-led air strikes from 25 March, as well as 11 other sites controlled by IS. Tikrit is a stronghold of the terror group which has been weakened by the joint efforts of the alliance.