Russian-installed separatists in eastern Ukraine said at least six civilians had been killed and six more injured in a missile strike on a market in the centre of Donetsk on Thursday.

"Ukraine's military are firing on the centre of Donetsk," the military headquarters of the self-proclaimed Donetsk People's Republic (DPR) said in a post on social media.

"According to the information received, six people were killed and six people were injured," Alexei Kulemzin, the Russian-installed mayor of Donetsk, said in a post on his Telegram channel.

Reuters was unable immediately to verify reports from the conflict zone. (Reporting by Reuters; Editing by Kevin Liffey)