Armenia says one of its fighter jets was shot down by a Turkey jet, in a major escalation of a conflict over the disputed Nagorno-Karabakh region.
The Armenian foreign ministry said the pilot of the Soviet-made SU-25 died after being hit by the Turkish F-16 in Armenian air space.
Turkey, which is backing Azerbaijan in the conflict, has made no comments.
Nearly 100 people, including civilians, have died in three days of fighting over the disputed mountainous region.
The mountainous enclave is officially part of Azerbaijan, but has been run by ethnic Armenians since 1994.
The fighting that started three days ago now appears to be spilling out of Nagorno-Karabakh.