A major prisoner exchange between Russia, the US and four European countries is under way in Ankara, the Turkish presidency has confirmed.

Three US citizens imprisoned in Russia - Wall Street Journal reporter Evan Gershkovich, US Marine veteran Paul Whelan and Russian-American radio journalist Alsu Kurmasheva - are thought to be among those being released.

In total, the exchange will involve at least 24 prisoners.

Eight Russian nationals are expected to be returned to Russia, including several with suspected ties to Russian intelligence.

One of them is Vadim Krasikov, identified by German officials as a colonel in Russia’s FSB intelligence service, who is serving a life sentence for the 2019 murder of a Kremlin opponent in a Berlin Park.

Turkey's presidency said in a statement that the exchange involved 26 individuals held in prison in seven countries - the US, Germany, Poland, Slovenia, Norway, Russia and Belarus.

Ten prisoners including two minors were relocated to Russia, 13 to Germany and three to the US, it added.

It is thought the children mentioned are those of Artyom Dultsev and Anna Dultseva, a Russian couple recently convicted of spying in Slovenia, who are thought to be among those being swapped.

The Turkish presidency said all the prisoners were taken off aircraft, moved to secure locations under the supervision of Turkish security officials, then put on planes for their respective destination countries.

The swap comes after days of speculation about a major swap between various countries, which increased after several dissidents and journalists jailed in Russia were moved from their prison cells to unknown locations.

Vladimir Kara-Murza, a Kremlin opponent with dual Russian-British citizenship, is one of those detainees whose whereabouts are unknown which has fuelled expectations that he too could be released.

Others potentially on the list are Russian opposition politician Ilya Yashin and veteran human rights campaigner Oleg Orlov.

Although secret prison transfers are common in Russia, the multiple "disappearance" of well-known prisoners was unusual.

Earlier this week, Belarusian leader Alexander Lukashenko pardoned a German citizen Rico Krieger who had been sentenced to death for terrorism and other charges.

If all the releases take place, it will be one of the biggest exchanges between Russia and the West in history.

The last high-profile prisoner swap took place in December 2022, when US basketball star Brittney Griner was exchanged on the tarmac at Abu Dhabi airport for notorious Russian arms dealer Viktor Bout, who had been held in an American prison for 12 years.

The last comparable one occurred in Vienna in 2010, when 10 Russian spies held in the US were swapped for four alleged double agents held in Russia.

One of them was Sergei Skripal, a former military intelligence officer, later poisoned by nerve agent Novichok in Salisbury in 2018.

Tensions between Moscow and the West have been high in recent years, especially since the Russian invasion of Ukraine in February 2022.