Russia has likely been recruiting Cuban nationals to fight in its army in Ukraine, research by the BBC has shown.

In September and October 2023, passport details belonging to over 200 Cubans who allegedly joined the Russian army were leaked online by a pro-Ukrainian platform called InformNapalm.

The passport details were obtained, the site said, by hacking the emails of a Russian military recruitment officer in Tula, south of Moscow.

A Facebook search has shown that 31 of the names mentioned in the Ukrainian leak match accounts whose owners appear to be in Russia or linked to the Russian army.

Some, for instance, have posted photos of themselves wearing Russian military uniform, or in locations that bear Russian street signs or Russian number plates. Others list Russia as their current place of residence.

Many of those Facebook users started posting Russia-related content in the second half of 2023, indicating when they might have arrived in the country.

Since launching its full-scale invasion of Ukraine, Russia has suffered heavy losses on the battlefield. A BBC investigation confirmed the names of more than 50,000 Russian troops killed in Ukraine - but the real number is likely to be much higher. Ukraine's own estimate puts the number of Russian soldiers killed or wounded in the war at nearly 500,000.

Recruiting foreigners to replace some of the losses also helps the Kremlin avoid the risks posed by trying to mobilise Russians by force. When Russia declared a partial mobilisation in 2022, hundreds of thousands of men left the country.

Bringing Cubans into Russia is relatively straightforward. The two countries have been allies since the Cold War, Cubans do not need a visa to travel to Russia and direct flights to Moscow make the trip easier.

Meanwhile, lucrative army contracts offered by Russia appeal to Cuban men desperate to escape the worsening economic crisis on the US-sanctioned island.

Documents leaked online and media reports suggest Cuban men are offered monthly payments in the region of $2,000 (£1,600) per month - a huge sum for Cuba, where the average monthly salary is under $25 (£20).

The promise of Russian citizenship may also entice some Cubans.

Cubans are being enticed by lucrative rewards and Russian passports. (This man's face is blurred to protect his identity)

Since the start of its war against Ukraine, Moscow has been taking steps to make it significantly easier for foreigners to obtain Russian citizenship after spending time in the army, and the BBC has seen social media posts suggesting that some Cuban fighters received Russian passports within months of signing up.

A Russian passport allows visa-free travel to 117 destinations, while Cuban passport holders are limited to 61.

A local media outlet in the city of Ryazan, near Moscow, confirmed that Cubans are joining the Russian army.

The Cubans wanted to "help our country achieve the objectives of the special military operation", it reported, adding that "some of them would like to become Russian citizens in the future".

But finding a reliable estimate of the number of Cubans who have joined the Russian ranks is difficult.

Ukraine's diplomatic envoy for Latin America and the Caribbean, Ruslan Spirin, put the number at 400 in an interview with the Wall Street Journal.

One Cuban officer in Russia, Lázaro Gonzalez, told an exiled anti-government radio station that 90 Cubans were serving under his command.

According to him, they were likely to be deployed to already occupied parts of eastern Ukraine rather than frontline positions.

"As the Russian army occupies areas in Ukraine, what we Cubans do is support the army in those cities and in those areas that are occupied, that's all," Mr Gonzalez told the Miami-based radio station.

Last year, Marilin Vinent showed a photo of her son Dannys in uniform, saying he had gone to Russia for a construction job

Numerous reports suggest Cubans have often joined the Russian army after coming into contact with recruiters on social media, but that not all of them appeared aware of the real nature of the job on offer.

A popular Cuban YouTube content creator told a story last year of two 19-year-olds from Cuba who claimed they had been offered construction jobs in Russia, but were instead sent to the front line in Ukraine.

Their case reflects the experiences of other foreigners who told the BBC they were lured to Russia by the promise of higher salaries - only to end up on the battlefield.

For their part, Cuban authorities have issued conflicting statements on their citizens' involvement in the Ukraine war.

Following a flurry of reporting in September 2023 about Cubans fighting in Ukraine, authorities in Havana said they had arrested 17 people involved in their recruitment.

However, soon afterwards, Cuba's ambassador to Russia, Julio Antonio Garmendía Peña, said his government had nothing against Cubans who wanted to "simply sign a contract and legally take part in this operation alongside the Russian army".

Hours later, Foreign Minister Bruno Rodríguez Parrilla said Havana was against "the participation of Cuban citizens in conflicts of any sort".

Cuba's Foreign Minister, Bruno Rodríguez Parrilla, met his Russian counterpart Sergei Lavrov in Havana last year

Meanwhile, Ukrainian authorities have said they have seen an increase in the number of foreign fighters joining Russian forces in recent months, as well as foreigners among the soldiers the Ukrainian army has captured on the battlefield.

Petro Yatsenko, a spokesman for Ukraine's agency for prisoners of war, told the BBC many of them came from low-income countries such as Cuba, India and Nepal, as well as African and Central Asian states.

"Every week we capture up to five persons from foreign countries on the frontline as prisoners of war," he said.

Their skills as fighters were low, he added, which meant their life expectancy on the battlefield was not even days, but hours.