France said on Tuesday it was working with its partners to respond strongly after what it said was an unjustified military operation launched by Azerbaijan on Nagorno-Karabakh.

“France calls on Azerbaijan to immediately cease its offensive and return to respect for international law,” the foreign ministry said in a statement.

“It will hold Azerbaijan solely responsible for the fate of the civilian populations of Nagorno-Karabakh.”

It called for the United Nations Security Council to convene urgently to discuss the issue.

France, along with the United States and Russia are co-chairs of the Organization for Security and Co-operation in Europe’s (OSCE) Minsk Group that mediates over Nagorno-Karabakh.

“It (France) is working closely with its European and American partners so that a strong response is provided to this unacceptable offensive, commensurate with the risks it poses to the security of the region,” the ministry said.

Azerbaijan on Tuesday launched “anti-terrorist activities” in the Nagorno-Karabakh region, saying its aim was to restore constitutional order and drive out what it called Armenian military formations there.