Vladimir Putin was greeted with a display of a Ukrainian flag while visiting Kazakhstan for a summit where he is expected to discuss the war in Ukraine.

Ukraine's flag - with its horizontal bands of blue and yellow - briefly appeared late on Wednesday instead of the Russian white, blue and red tricolor on a screen located on one of Astana's main thoroughfares.

Russia may use its new Oreshnik hypersonic missile to attack "decision-making centres" in Kyiv in response to Ukraine's firing of Western missiles at Russian territory, President Vladimir Putin said on Thursday.

A nationwide air raid alert was sounded in Ukraine early on Thursday, with reports of explosions in several cities. The Ukrainian air force said in a Telegram post at 05:19 local time (03:19 GMT) that the alert was in force "throughout the territory of Ukraine due to the threat of missile danger".

President Vladimir Putin warned that his forces could strike “decision-making centers” in the Ukrainian capital of Kyiv with new ballistic missiles as retaliation for attacks on Russia using Western missiles.