Heavy fighting has erupted between Armenia and Azerbaijan over the disputed Nagorno-Karabakh region, with both civilians and combatants killed. Accusing Azerbaijan of air and artillery attacks, Armenia reported downing helicopters and destroying tanks, and declared martial law. Azerbaijan said it had begun a counter-offensive in response to shelling. The region is internationally recognised as part of Azerbaijan but controlled by ethnic Armenians. They broke away in the dying years of the Soviet Union. Both Armenia and Azerbaijan were part of the communist state, which sought to suppress ethnic and religious differences. Amid the clashes, Azerbaijani President Ilham Aliyev said he was confident of regaining control over the breakaway region. Martial law has also been declared in some regions of Azerbaijan. The conflict in the Caucasus Mountains has remained unresolved for more than three decades, with periodic bouts of fighting. Border clashes in July killed at least 16 people, prompting the largest demonstration for years in the Azerbaijani capital Baku, where there were calls for the region's recapture. On Sunday, Turkey's President Recep Tayyip Erdogan pledged support for Azerbaijan during the new crisis while Russia, traditionally seen as an ally of Armenia, called for an immediate ceasefire and talks to stabilise the situation. France, which has a large Armenian community, called for an immediate ceasefire and dialogue, while Iran, which borders both Azerbaijan and Armenia. offered to broker peace talks.