• Economist Sergei Guriev on Friday warned that Russia could become like "North Korea on steroids" when President Vladimir Putin is replaced.
• "It's very hard to predict what will come after Putin. The reason for that is Putin has built his regime in a way nobody can replace him," Guriev said.
• A former adviser to the Russian government, Guriev abruptly left the country in 2013 amid a political crackdown.

Economist and former Kremlin advisor Sergei Guriev on Friday warned that Russia could become like "North Korea on steroids" when President Vladimir Putin is replaced, saying the current political system would likely collapse when a new leader takes the reins.

His comments come ahead of the funeral of the Soviet Union's last leader Mikhail Gorbachev on Saturday.

Putin, who paid his respects to Gorbachev at the Moscow hospital where the 91-year-old died on Tuesday, will not attend the service.

Putin is known to have had a strained relationship with Gorbachev, who ushered in sweeping reforms that ultimately led to the fall of the Soviet Union.

Speaking to CNBC's Steve Sedgwick at the Ambrosetti Forum in Italy, Guriev said it was extremely difficult to predict what might happen when Putin is eventually replaced as president.

"Regimes like this change in very unpredictable ways," Guriev said. "It's very hard to predict what will come after Putin. The reason for that is Putin has built his regime in a way nobody can replace him."

"He built the regime in a way that without him, the system will not function. People around him don't trust each other, sometimes hate each other, so if he is gone the system will change somehow," he said.

"So, probably initially it will be some kind of ultra-nationalist guy or military junta, but it will not last for long exactly because the system is built around Putin. And eventually, I think the system will collapse," Guriev said.

"It could be months, it could be several years, it could be North Korea on steroids, who knows? But it could also be a situation where the system collapses and somebody who wants to rebuild the economy reaches out to the West," he added.

The Russian Embassy in London and Russia's Foreign Ministry were not immediately available to comment when contacted by CNBC on Friday.

Guriev, a former adviser to the Russian government, abruptly left the country in 2013 amid a political crackdown and fled to France.

Putin later said that Guriev would be welcome to return to Russia, adding that the economist's departure could not be associated with any activities of the authorities.

Putin, 69, signed a law last year that could pave the way for him to run for the office twice more in his lifetime. The legislation may mean he is able to stay in office through to 2036.