First Nagorno-Karabakh War
As the situation was escalating, the neighboring countries mediated a peace agreement between Republic of Armenia and Republic of Azerbaijan; Boris Yeltsin visited Stepanakert in September 1991 with the then Kazakh President, Nursultan Nazarbayev, and what is called Zheleznovodsk declaration was adopted. However, on 20 November in Martuni, Vagif Jafarov, who was the head of Shusha, as well as Russian and Kazakh officials who were in charge of the implementation of the peace agreement, were killed in a helicopter crash that was caused by Armenian fighters. In response, the Azerbaijani National Council declared on 26 November that Nagorno-Karabakh was under the Azerbaijani sovereignty and that Stepanakert was now Khankendi, although Armenians in the region held a referendum on 10 December with support from Armenia; 108,615 people voted for the region's independence, while there were no Azerbaijanis voting.