Azerbaijan’s defence ministry said in a statement that Armenian forces had opened fire with machine guns and grenade launchers in the direction of a village in the Kelbajar region, and had thrown hand grenades. It said its forces returned fire.

The ceasefire was  called on Wednesday after some of the heaviest border clashes since last year’s six-week war between ethnic Armenian forces and Azeri troops over the disputed Nagorno-Karabakh region and surrounding areas.

Armenia said three of its soldiers had been killed and two wounded. Azerbaijan said two of its soldiers had been wounded.

Last year, in fighting from September to November, Azeri troops drove ethnic Armenian forces out of swaths of territory they had controlled since the 1990s in and around the Nagorno-Karabakh region, before Russia brokered a ceasefire.

A simmering border dispute between the two has since flared up, with both sides accusing each other of separate incursions into each others’ territory in recent months, highlighting the fragility of the ceasefire.

Moscow has deployed some 2,000 peacekeepers in the area to oversee the November agreement.