By Andrew Osborn

LONDON Russian mercenary chief Yevgeny Prigozhin said on Saturday that his Wagner fighters had completed the capture of the Ukrainian city of Bakhmut after months of intense fighting, a claim denied by Ukraine.

Here is a look at the significance for both sides of the largely ruined city at the centre of the war's longest, bloodiest battle.

SPRINGBOARD?

A regional transport and logistics hub, Bakhmut is in Ukraine's Donetsk, part of the largely Russian-speaking industrialised Donbas region which Moscow wants to annex with its self-declared "special military operation".

U.S. Pentagon chief Lloyd Austin and NATO alliance head Jens Stoltenberg have played down its potential fall as symbolic, as have Western military experts.

But Bakhmut's capture, if confirmed, would put within easy range of Russian artillery two bigger cities in the Donetsk region - Kramatorsk and Sloviansk - that Russia has long coveted. Moscow needs to control both to complete what it calls its "liberation" of the "People's Republic of Donetsk."

UKrainian President Volodymyr Zelenskiy told CNN in March that he feared Russian forces would have "an open road" to the two cities if they took Bakhmut, and said his order to hold it was a tactical decision.

The nearby town of Chasiv Yar, west of Bakhmut, would probably be next to come under Russian attack, though it is on higher ground and Ukrainian forces are believed to have built defensive fortifications nearby.

Western analysts and diplomats are sceptical that Russian forces would be able to swiftly capitalise on Bakhmut's capture given that they began shelling the city a year ago, launched a ground assault in August and have suffered major losses since.

Russia's chaotic withdrawal from Ukraine's northeast last year also deprived it of territory that would have made it easier for its forces to seize cities like Sloviansk once they had control of Bakhmut.

KILLING ZONE?

Ukraine and Russia have both said the battle for Bakhmut, which Moscow calls by its Soviet-era name Artyomovsk, has been important to destroy and distract each other's forces ahead of an expected major Ukrainian counter-offensive.

Reminiscent of World War One, fighting involved trenches and relentless artillery and rocket strikes across a heavily-mined battlefield as well as house-to-house clashes and air attacks which destroyed much of the city.

Most of the pre-war population of 70,000-80,000 had long since fled. The International Committee of the Red Cross (ICRC) said those left were eking out an existence in underground shelters under heavy shelling.

Images of battlefields strewn with corpses from both sides surfaced on social media. Casualty figures are classified, but U.S. officials estimate that tens of thousands of Russian soldiers - many of them convicts recruited by Wagner - were killed. Russian officials alleged high Ukrainian losses too.

Reuters is unable to verify battlefield casualty figures.

Prigozhin, whose Wagner forces led the battle for the Russians, published numerous pictures of his own dead fighters, often as part of an attempt to lobby Russia's defence ministry for more ammunition.

Zelenskiy portrayed "Fortress Bakhmut" as a symbol of defiance which he said was bleeding the Russian military dry. His aide Mykhailo Podolyak said the battle had pinned down some of Russia's best units and degraded them ahead of Ukraine's planned Western-backed spring push back.

Konrad Muzyka, a Polish military analyst who visited the Bakhmut area with colleagues in March, said after his trip he thought it no longer made military sense to hold the city given what he said was the scale and cost of Ukrainian losses.

The city has witnessed slaughter before: during World War Two, occupying Nazi troops herded 3,000 Jews into a nearby mine shaft and bricked it up, suffocating them.

PSYCHOLOGICAL BOOST?

If confirmed, Bakhmut would be Russia's first major capture since July last year and a morale-boosting battlefield win after a string of defeats.

Its loss could sap morale in Ukraine, even if - as Kyiv's allies say - it has little strategic value.

Retaining the city had helped sustain support from Western countries, proving it was making a difference, according to Michael Kofman, an expert on the Russian military at the U.S.-based CNA think-tank.

Zelenskiy gave the U.S. Congress a battle flag signed by the city's defenders when he visited in December and told the Associated Press in March he feared a Russian victory in Bakhmut would spark calls from the international community and his own country to sue for peace, something he does not want to do.

Ukraine can take comfort from the fact that it held off Russian forces for so long and extracted such a high price for Bakhmut however, suggesting any Russian attempt to take more territory will be similarly costly.

WIN FOR WAGNER?

The city's capture would be a boost for Russia's most high-profile mercenaries - Wagner - and their publicity-hungry founder Prigozhin.

The 61-year-old former convict and catering tycoon, who is sanctioned in the West, has been seeking to parlay his outfit's battlefield success into political influence.

While mounting evidence suggests the Kremlin has moved to curb what it sees as his excessive political clout, nobody could dispute that Wagner mercenaries, including convicts recruited by Prigozhin, have played a major role as assault troops.

Some Western military experts believe Ukraine's goal was to destroy Wagner as a fighting force in Bakhmut and Prigozhin has admitted that his mercenary force would need extra support from the regular army to keep advancing beyond Bakhmut.

(Reporting and writing by Andrew Osborn; Editing by Philippa Fletcher)