The Donetsk and Luhansk regions, collectively known as the Donbass, are combat zones between pro-Russian separatists and the Ukrainian military in a conflict that broke out in April 2014. More than 13,000 people have been killed in the war, and the sides regularly accuse each other of violating an internationally brokered ceasefire there.

The head of one of eastern Ukraine’s breakaway regions has said his separatist-held republic wants to join Russia as a full-fledged member.

“The Donbass must return to its homeland as a full member,” Denis Pushilin, the head of Donetsk, said in an interview with local media on Sunday. “The Donbass looks toward Russia today.”

Sunday marked the fifth anniversary of the self-proclaimed Donetsk People's Republic, known equally by the abbreviations DNR and DPR. Russia recognizes passports issued in the separatist-held areas, and the Russian ruble is already a commonly used currency.

Addressing the flag-waving crowd that day, Pushilin said the DNR’s main goal is to accede to Russia like Crimea did in 2014.

“Of course we’d like the integration to go faster,” Pushilin said. “But we understand there are geopolitical implications, and we know our path is thornier [than Crimea’s], yet the goal is clear and we’re getting there.”

Reuters contributed reporting to this article.