Azerbaijan and Armenia both declared martial law early Sunday after clashes killed at least 16 military members and several civilians.
The two countries, both former Soviet republics, experienced their heaviest clash since 2016 on Sunday over Nagorno-Karabakh, a disputed territory that is inside Azerbaijan but run by ethnic Armenians, Reuters reported.
Armenia accused Azerbaijan of an air and artillery strike on the area, with Nagorno-Karabakh saying 16 of its military members were killed and more than 100 were wounded in the attack. Armenian activists also said an ethnic Armenian woman and child were killed.
Armenia also said Azeri troops attacked civilian targets, prompting Armenia to vow for a “proportionate response.”
Armenian Prime Minister Nikol Pashinyan tweeted the decision for Armenia to declare martial law after the strike.
Azerbaijan also declared martial law and asserted its attack was in response to Armenian shelling, which killed five members of one family, according to Reuters. It also claimed to have taken over up to seven villages, which Nagorno-Karabakh initially denied but added later it had lost “some positions.”
Azerbaijan denied Armenian assertions that Azeri helicopters and tanks were demolished and said Armenia was conducting “deliberate and targeted” strikes along the front line.
Azerbaijani President Ilham Aliyev said the Armenian military “fired on our settlements as well as our military positions,” adding the Azerbaijani army “is currently firing on the enemy’s military position, and as a result of these strikes, many units of the enemy’s military equipment have been destroyed,” according to Politico’s translation of a state agency report.
In response to Sunday’s conflict, Russia called for the countries to declare a ceasefire, while Turkey said it would back Azerbaijan in any head-to-head, Reuters reported. The European Union and the Organization for Secretary and Cooperation in Europe both encouraged the countries to disengage attacks and go back to negotiations.
The violence came after tensions between majority Christian Armenia and mostly Muslim Azerbaijan erupted into a war in the 1990s as the Soviet Union collapsed and as Nagorno-Karabakh broke away from Azerbaijan in 1991. Clashes have continued over the years, including in 2016 when at least 200 people were killed and in July when at least 16 people were killed.
Nagorno-Karabakh sits nearby pipelines that send Caspian oil and natural gas from Azerbaijan to the rest of the world, Reuters noted.