The superyacht was spotted in Montenegro on Saturday morning.

The news was reported by the Daily Mail.

Russian billionaires have been moving their assets around the world to prevent them from being seized.

The vessel left a Spanish shipyard on Tuesday for repairs, which had been done late in the year.

According to SuperYacht Fan, the $600 million yacht was spotted off the coast of Tivat in Montenegro on Saturday.

In the early hours of Saturday, the site MarineTraffic showed that Solaris was heading around Sicily and into the Ionian Sea.

The port agents in Tivat, the BCM Group, did not respond to the request for comment made outside of normal working hours.

It is not an EU member yet. The Turkish news agency Anadolu Agency reported earlier this month that Montenegro had joined the EU's sanctions on Russia.

The US and EU are isolating Russia from the rest of the world. This includes banning the export of luxury goods to Russia.

The eighth richest man in Russia is worth more than $11 billion. He has stakes in the Russian steel company and Norilsk nickel.