The parents of Russian oil tycoon and fierce Kremlin critic Mikhail Khodorkovsky are set to arrive in Germany later in the day, according to muliple reports.

Following his surprise release from a Russian jail after being pardoned by President Vladimir Putin, Khodorkovsky has landed in Berlin.

The one-time Russian oligarch was welcomed by former German foreign minister Hans-Dietrich Genscher as he touched down the Berlin airport at about 15:00 local time on Friday (20 December).

German Chancellor Angela Merkel was reportedly "delighted" upon hearing the news of Khodorkovsky's release and his subsequent arrival in Berlin.

"My father is free and safe in Germany. Thanks to all of you for the support that you have given my family in recent years," said the tycoon's son Pavel Khodorkovsky.

Previous reports said Khodorkovsky's mother Maria Khodorkovskaya was already in Germany but they were later refuted.

Maria is being treated for cancer and is widely believed to be in poor health.

Khodorkovsky's wife lives in Switzerland.

Khodorkovsky, once Russia's richest man, was believed to be travelling in a private jet lent by German businessman Ulrich Bettermann, the chief of OBO Bettermann, which has widespread operations in Russia.

"None of us can judge these releases in the end. There's obviously a time factor involved. I don't want to belittle it, the fact people are now being released is a good signal. I say we should use them to have further discussions with Russia about legal processes and the protection of human rights," said German Foreign Minister Frank-Walter Steinmeir.

The Kremlin critic had earlier said in a statement he was asking for a pardon citing family reasons but had not admitted any guilt.

He said: "I would like to thank everyone who has been following the Yukos case all these years and for support you have rendered me, my family, and all those who have been convicted unjustly and who are still being persecuted. I am really looking forward to the minute when I can hug my loved ones and personally shake hands with all of my friends and colleagues."

Meanwhile, US Sectretary of State John Kerry has welcomed Russia's move to free Khodorkovsky.

"We have repeatedly expressed our concerns about due process violations and selective prosecution in Russia, including against Khodorkovsky and his business partner Platon Lebedev, who remains in prison," Kerry said in a statement.