As rumours continue to swirl about a potential international prisoner swap, it has now emerged that the names of several Russians serving prison sentences in the US have disappeared from the US Bureau of Prisons database.

Lawyer Igor Slabykh, who writes about US legal news, noticed that the names of Alexander Vinnik, Maxim Marchenko, Vadim Konoshchenko, Vladislav Klushin and Roman Seleznyov, all serving sentences in American jails, no longer appeared on the online database as of Wednesday.

Russian state-run news agency RIA Novosti wrote that other Russians serving sentences in American prisons did still appear on the database, however, such as hacker Vladimir Dunayev.

In the past 72 hours, at least 10 political prisoners being held in Russian jails have been reportedly transferred without any prior notice to an unknown location. The list includes both high-profile Russian prisoners, including at least one with dual nationality, one US citizen, and one foreign-born Russian citizen.

Belarusian dictator Alexander Lukashenko also pardoned a German prisoner, Rico Krieger, who had been sentenced to death in the country at the end of June, on Tuesday.