Founder of Wagner private mercenary group Yevgeny Prigozhin makes a statement as he stand next to Wagner fighters in the course of Russia-Ukraine conflict in Bakhmut, Ukraine, in this still image taken from video released May 20, 2023. Press service of "Concord"/Handout via REUTERS

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, reports Reuters.

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.

Kyiv denied Prigozhin's claim earlier on Saturday, but did not have an immediate response to the defence ministry's 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.

The claims came after a week in which Ukrainian forces have made their most rapid gains for six months on Bakhmut's northern and southern flanks.

Prigozhin, who has repeatedly denounced Russia's regular military for abandoning ground captured earlier by his men, said his own forces would pull out of Bakhmut in five days to rest, handing the ruins over to the regular military.

"Today, at 12 noon, Bakhmut was completely taken," Prigozhin said in a video in which he appeared in combat fatigues in front of a line of fighters holding Russian flags and Wagner banners. "We completely took the whole city, from house to house."

Ukrainian military spokesperson Serhiy Cherevatyi, reacting to Prigozhin's comments before Russia's announcement, had told Reuters: "This is not true. Our units are fighting in Bakhmut."

SPLIT BETWEEN WAGNER, RUSSIAN FORCES

Whether the Ukrainian forces have left Bakhmut or not, they have been slowly pulling back inside it, to clusters of buildings on the city's western edge.

Meanwhile, to the north and south, they have seized swathes of territory from Russian troops.

Russia has acknowledged losing some ground around Bakhmut in the past week, while denying assertions by Prigozhin that the flanks around the city guarded by regular troops have collapsed.

Kyiv says its aim in Bakhmut has been to draw Russian forces from elsewhere on the front into the city, to inflict high casualties there and weaken Moscow's defensive line elsewhere ahead of a planned major counteroffensive.

The battle for Bakhmut has revealed a deepening split between Wagner, a mercenary force that has recruited thousands of convicts from Russian prisons, and the regular Russian military. For two weeks, Prigozhin has been issuing daily video and audio messages denouncing Russia's military leadership, often in expletive-laden rants.

In Saturday's video he said that because of the "whims" of Defence Minister Sergei Shoigu and Chief of Staff Valery Gerasimov, "five times more guys died than they should have". He thanked Putin "that he gave us this chance and great honour to defend our motherland".

Moscow has long claimed that capturing Bakhmut would be a stepping stone towards advancing deeper into the Donbas region it claims to have annexed from Ukraine. It has made it the principal target of a massive offensive that failed to capture any significant ground elsewhere.

Prigozhin has acknowledged that Bakhmut, formerly a city of 70,000 people, has little strategic significance, despite its huge symbolic importance because of the scale of losses in Europe's bloodiest ground battle since World War Two.

KYIV PREPARES COUNTEROFFENSIVE

Saturday's claims came as Kyiv prepared its counteroffensive, the next major phase in the war after six months during which it kept its forces on the defensive while weathering Russia's big offensive.

President Volodymyr Zelenskiy attended the G7 summit of major industrial powers in Japan on Saturday, winning pledges of support including a signal from Washington that it would now back the training of Ukrainian pilots to fly F-16 warplanes. Previously, sending combat aircraft had been a taboo.

En route to Japan, Zelenskiy stopped at an Arab summit in Saudi Arabia.

The Vatican said on Saturday that Pope Francis had asked Cardinal Matteo Zuppi, head of the Italian bishops' conference, to carry out a peace mission to try to help end the war.