Turkish President Tayyip Erdogan said on Monday Armenia must immediately withdraw from territory he said it was occupying in Azerbaijan, and it was time to end a crisis over the breakaway region after clashes between Azeri and Armenian forces.
At least 21 people were killed on Monday in a second day of fierce fighting over Nagorno-Karabakh, a region inside Azerbaijan run by ethnic Armenians. Ankara has pledged support for Azerbaijan in the conflict.
"It is time to end the crisis in the region, which started with the occupation of Nagorno-Karabakh. The region will once again see peace after Armenia immediately withdraws from the Azeri lands it is occupying," Erdogan told an event in Istanbul.
He said the Minsk group - which is led by Russia, France and the United States and mediates between Armenia and Azerbaijan - had failed to solve the issue for almost 30 years.
Azerbaijan "had to take matters into its own hands whether it likes it or not," Erdogan said.
"Turkey will continue to stand with...Azerbaijan with all its resources and heart."
He did not directly address whether Turkey was currently playing an active role in the conflict, as Armenia has said. Azerbaijan denies the claim.
The fighting reportedly involves air power and heavy armour.
Earlier, Turkish Defence Minister Hulusi Akar said Armenia must send back foreign "mercenaries and terrorists" to achieve stability in region.
Ethnic Armenians who make up the vast majority of the population of Nagorno-Karabakh reject Azeri rule. Yerevan and Baku frequently accuse each other of attacks in the region despite a 1994 ceasefire.