Denying that the alleged killings of Armenians in Ottoman Turkey in 1915were genocide is not a criminal offence, the European Court of Justice ruled onTuesday in a case involving Switzerland.

The court, which upholds the 47-nation European Convention on HumanRights, said a Swiss law against genocide denial violated the principle offreedom of expression, Reuters reported.

The ruling has implications for other European states such as Francewhich have tried to criminalize the refusal to apply the term"genocide" to the alleged massacres of Armenians during the breakupof the Ottoman empire.

A Swiss court had fined the leader of the leftist Turkish Workers'Party, Dogu Perincek, for having branded talk of an Armenian genocide "aninternational lie" during a 2007 lecture tour in Switzerland.

Turkey accepts that many Armenians died in partisan fighting beginningin 1915 but denies that up to 1.5 million were killed and that it constitutedan act of genocide.

"Genocide is a very narrowly defined legal notion which isdifficult to prove," the court said.

"Mr Perincek was making a speech of a historical, legal andpolitical nature in a contradictory debate."

The court drew a distinction between the Armenian case and appeals ithas rejected against convictions for denying the Nazi German Holocaust againstthe Jews during World War Two.

"In those cases, the plaintiffs had denied sometimes very concretehistorical facts such as the existence of gas chambers," the court said."They denied crimes committed by the Nazi regime that had a clear legalbasis. Furthermore, the facts they denied had been clearly been established byan international tribunal."

The judges cited a 2012 ruling by France's Constitutional Council whichstruck down a law enacted by then President Nicolas Sarkozy's government as"an unconstitutional violation of the right to freedom of speech andcommunication".

Switzerland has three months to appeal against the ruling.