Russia claimed on Saturday to have fully captured the smashed eastern Ukrainian city of Bakhmut, which would mark an end to the longest and bloodiest battle of the 15-month war.

The assault on the largely levelled city was led by troops from the Wagner Group of mercenaries, whose leader Yevgeny Prigozhin said earlier in the day that his troops had finally pushed the Ukrainians out of the last built-up area inside the city.

Taking Bakhmut - which Russia refers to by its Soviet-era name of Artyomovsk - would represent Moscow's first big victory in the conflict in more than 10 months.

"As a result of offensive actions by Wagner assault units, supported by artillery and aviation of the Southern Group of Forces, the liberation of Artyomovsk has been completed," the Russian defence ministry said in a one-line statement.

Russian President Vladimir Putin congratulated troops on capturing the city and said those who had distinguished themselves would be given awards, domestic Russian news agencies reported.