"Rest assured that French authorities are determined to get to the bottom of these intolerable acts, " he said.

BBC: Kurdish PKK co-founder Sakine Cansiz shot dead in Paris

"Rest assured that French authorities are determined to get to the bottom of these intolerable acts, " French Interior Minister Manuel Valls said, adding that the killings were "surely an execution".

BBC: Police hunt killers of PKK co-founder Sakine Cansiz

He said Mr Assad's regime had conducted itself in an "unacceptable, intolerable way" and had committed acts that disqualified it from power.

BBC: Syria conflict: Russia's Vladimir Putin stands firm