Several engineers working at Russia's top nuclear research facility, the All-Russian Research Institute of Experimental Physics, have been arrested for attempting to use one of the country's most powerful supercomputers to secretly mine bitcoin.

"Their activities were stopped in time," Tatyana Zalesskaya, a spokeswoman for The Federal Nuclear Centre in Sarov, western Russia, told Interfax news agency on Friday (9 February) and added that a criminal case has been opened against them all. She, however, did not reveal how many employees of the nuclear facility were arrested.

The facility is a secretive "closed" city about 500km east of Moscow where nuclear weapons research has been conducted since 1946. The city was previously unmarked on Soviet maps and is the birthplace of the USSR's first nuclear bomb. Guarded by the Russian military and barbed wire fences, the city is still restricted and requires special permits for Russians to visit.

The nuclear facility employs up to 20,000 people and houses a 1-petraflop supercomputer capable of performing around 1,000 trillion calculations per second. It was first switched on in 2011 making it the 12th most powerful in the world.

Due to security concerns, none of the institutes' computers are supposed to be connected to the Internet. Russian news services reported that the accused engineers attempted to connect the supercomputer to the internet to mine cryptocurrency. Their actions were immediately detected by the nuclear centre's security department.

They have reportedly been handed over to the Federal Security Service (FSB).

"There has been an unsanctioned attempt to use computer facilities for private purposes including so-called mining," the nuclear centre said in a statement. "As far as we know, a criminal case has been initiated against them.

"Similar attempts have recently been registered in a number of large companies with large computing capacities, which will be severely suppressed at our enterprises, this is technically a hopeless and criminal offense," the statement added.

This isn't the first time industrial facilities in Russia have been used to mine cryptocurrency as Russian lawmakers moved to regulate the burgeoning yet volatile digital currency market.

Last month, a Russian businessman named Aleksey Kolesnik reportedly bought two power plants just for cryptocurrency mining. In December 2017, Russian pipeline giant Transneft said it discovered its computer systems were infected with a cryptomining malware to covertly mine Monero coins.