The Russian authorities were Friday urgently searching for the missing son of software tycoon Eugene Kaspersky who reports said is held by kidnappers demanding a ransom of 3 million euros ($4.4 million).

The interior ministry has not officially announced that Ivan Kaspersky, 20, has been abducted in what would be one of the highest-profile kidnappings in Russia in recent years.

But press reports Friday said that the student had been kidnapped by unknown abductors, saying the authorities had hoped to keep the matter secret until the news was leaked to a tabloid website on Thursday.

Kaspersky, 45, co-founded Kaspersky Lab in 1997, building on a decade of research into computer viruses. The company has emerged as one of the world's leading anti-virus software firms.

His fortune is now valued at $800 million by Forbes magazine, making him the 125th richest man in Russia.

The Kommersant daily said Ivan Kaspersky, a mathematics student at Moscow State University, was taken on Tuesday morning close to the office where he is currently doing work experience as a programmer.

It quoted a source as saying the kidnappers then phoned Eugene Kaspersky in London on his mobile phone, making the 3 million euro ransom demand and warning him not to contact the police.

He then flew to Moscow and requested help from his personal contacts in the Federal Security Service (FSB). The authorities kept the matter top secret to protect the security of Ivan Kaspersky.

However the lifenews.ru website reported the kidnapping on Thursday, apparently after one of Ivan's fellow students let slip the news in a conversation overheard by a journalist.

"That the information is now in the press is very bad," an official in the missing-persons department of Moscow police told the Izvestia newspaper which also confirmed the kidnapping.

"This can only be of harm to the kidnap victim."

The kidnappings of children of prominent businessmen is not uncommon in Russia, although Ivan Kaspersky appears to be the most prominent victim yet.

In 2009, criminals held the son of a vice president at state oil firm Rosneft, Mikhail Stavsky. He was freed unharmed after a three-month ordeal.

Viktoria Kisluk, the 16-year-old daughter of a top manager at Russia's biggest private oil firm Lukoil is still missing after vanishing in the Moscow region in March.