Armenia has asked Russia to help defend its borders after a clash with Azerbaijan forces in which it said 15 of its soldiers had been killed, 12 captured and two combat positions had been lost.

The fighting was the worst since a 44-day war last year, fought between ethnic Armenian forces and the Azeri army over the Nagorno-Karabakh enclave, which killed at least 6,500 people and ended in a decisive victory for Azerbaijan.

READ MORE:

Current education path 'unsustainable'

Diversifying Germany's forests

Poland urged to help migrants at Belarus border

In a series of statements published by Armenian and Russian news agencies, the Armenian defense ministry said its troops had come under fire from Azeri artillery.

"Since Azerbaijan has attacked Armenia's sovereign territory we are asking Russia to defend Armenia's territorial integrity based on an existing 1987 [mutual defense] agreement between our countries," said Armen Grigoryan, the secretary of Armenia's Security Council.

Russia has a military base in Armenia as well as a peacekeeping force in Nagorno-Karabakh but there was no immediate response from the Kremlin to the Armenian appeal.

The Azeri defense ministry said it had launched a military operation to respond to what it called large-scale "provocations" from the Armenian side and in a statement blamed Armenia's military-political leadership.

It said Armenian forces had shelled Azeri army positions with artillery and mortar fire and that its own operation had been successful.

"The Azerbaijan army has operational and tactical superiority," a statement claimed, confirming Azerbaijan had targeted Armenian troops and hardware along the border.

"Armenian servicemen are leaving their positions in fear and panic. Military equipment belonging to the opposing side has been destroyed."