Fierce fighting continues to rage following a flare-up of a decades-old conflict in the Caucasus region of south-eastern Europe. Dozens of deaths have been reported in battles between forces fighting for Armenia and Azerbaijan. At the heart of the conflict is a dispute over control of the mountainous region of Nagorno-Karabakh. It is recognised as part of Azerbaijan, but has been controlled by ethnic Armenians since a war ended in 1994. Tens of thousands of people died during the war and a million others were forced to leave their homes. Other countries are concerned that the latest fighting could spill out of the region and draw in neighbouring powers, including Turkey, Russia and Iran. They are also keen to maintain stability because major gas and oil pipelines run through the area. The latest intense fighting began on Sunday with both Armenia and Azerbaijan blaming each other for the escalation. Both parties said they had mobilised more soldiers and declared martial law in some areas. The fighting is the heaviest seen in the conflict since 2016, when at least 200 people were killed in clashes. Turkey has already declared its support for Azerbaijan, while Russia - which has military bases in Armenia but is also friendly with Azerbaijan - called for an immediate ceasefire. Armenia has accused Turkey of providing direct military support to help Azerbaijan gain control of territory, a claim denied by Azerbaijan. On Monday, Turkey's President Recep Tayyip Erdogan said Armenia must immediately end its "occupation" of the region, which he said would end the long crisis.