Mr Aslin, a former care worker from Newark-on-Trent, who has dual British and Ukrainian citizenship, moved to Ukraine after meeting now-wife Diane.
Russian proxies claimed he was a foreign mercenary, while Kyiv and Britain insisted he should be afforded protections under the Geneva Convention as a serving member of Ukraine’s armed forces.
Mr Aslin was captured alongside Shaun Pinner, 48, a former British Army soldier, and sentenced to death by firing squad by the self-proclaimed Donetsk People’s Republic earlier this year. Brahim Saadoun, a Moroccan, was also convicted in the same sham trial.
Alongside the five freed Britons, Saudi authorities on Wednesday announced the release of two Americans, one Moroccan, one Swede and one Croat.
They will soon be returned to their home countries, the Saudi foreign ministry said in a statement.
The identities of the other British nationals remained unclear.
The families of the two US nationals – Alexander Drueke, 39, and Andy Huynh, 27 – who were captured in June while fighting in Eastern Ukraine, confirmed their release.
Ann Linde, the Swedish foreign minister, confirmed a Swedish citizen, captured in May in the siege of the port city of Mariupol and facing a possible death sentence, was among those released.
Liz Truss, the Prime Minister, said: “Hugely welcome news that five British nationals held by Russian-backed proxies in eastern Ukraine are being safely returned, ending months of uncertainty and suffering for them and their families.
“I thank Volodymyr Zelensky for his efforts to secure the release of detainees, and Saudi Arabia for their assistance.”