Outbreak of fighting between Azerbaijan and Armenia over disputed territory kills 15 soldiers

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A sharp escalation in fighting between Azerbaijan and Armenia over the disputed territory of Nagorno-Karabakh has left 15 soldiers dead and prompted Russia to issue a call for calm.

Azerbaijan's Defense Ministry said Sunday that 12 of its troops have been killed in the past four days, including four overnight. Nagorno-Karabakh's armed forces said one of its soldiers was killed early Sunday, the third in recent days.

Azerbaijan's Nagorno-Karabakh region and some adjacent territory have been under the control of Armenian soldiers and ethnic Armenian local troops since the end of a six-year separatist war in 1994.

Both sides report frequent attacks along the cease-fire line, but the latest outbreak of fighting is the worst in many years.

Russia's Foreign Ministry said "a further escalation is unacceptable."