A Moscow court on Tuesday extended the house arrest of prominent US investor Michael Calvey and a French senior executive at his fund who are accused of defrauding a Russian bank.

The arrests of Calvey, the founder of multi-billion-dollar investment fund Baring Vostok, and French banker Philippe Delpal have raised serious concerns among foreign investors in Russia.

Moscow's Basmanny district court extended their house arrest to January 13, 2020, when their next hearing is due.

Calvey, Delpal and three other suspects are alleged to have defrauded Vostochny Bank of 2.5 billion rubles ($38.7 million) -- charges they say were fabricated by a competitor and relate to a shareholder dispute.

After they were detained in February, both were held behind bars for several months.

Calvey transferred to house arrest in April and Depal in August. Three of their Russian colleagues are still behind bars.

The arrests of American Michael Calvey (L), founder of multi-billion-dollar investment fund Baring Vostok, and French banker Philippe Delpal have raised serious concerns among foreign investors in Russia
The arrests of American Michael Calvey (L), founder of multi-billion-dollar investment fund Baring Vostok, and French banker Philippe Delpal have raised serious concerns among foreign investors in Russia AFP / Yuri KADOBNOV

Last week Russian authorities froze assets belonging to all five men.

On Tuesday, the court refused defence petitions to pay bail of five million rubles ($77,000) each for Calvey and Delpal or to soften the terms of their house arrest.

Delpal, who has lived in Russia for 15 years with his wife and their two daughters, criticised the "strict and draconian" terms of his house arrest.

"I've always said forcefully that I'm innocent, that there was no crime," he declared in court.

Calvey, who is highly respected in Russian investment circles, has worked in Russia for more than 20 years as head of Baring Vostok.

Russian President Vladimir Putin has brought up the detentions several times and French President Emmanuel Macron urged him to release Delpal at the G20 in Japan last June.

While arrests and criminal prosecution of business people in Russia are common, often launched by local authorities or competitors, it is rare for foreign investors to be targeted.