The statement, seen by CNN, said the "SY A" vessel is worth about EUR 530 million ($578 million) and was in storage at the northeastern port of Trieste.
It's one of the world’s largest superyachts, according to its manufacturer, Nobiskrug.
Melnichenko was sanctioned by the European Union on March 9 as part of expanded punitive measures against Russian oligarchs.
According to the EU, he owns the major fertilizer producer EuroChem Group and the coal company SUEK.
Read also: Italy seizes villas owned by propaganda TV host Soloviov, oligarch UsmanovThe EU Council decision, which authorized sanctions against Melnichenko, noted he and 36 other business leaders met with Russian President Vladimir Putin after the invasion of Ukraine began to discuss the potential economic impact of EU and US sanctions.
The EU Council decision reads: "The fact that he was invited to attend this meeting shows that he is a member of the closest circle of Vladimir Putin and that he is supporting or implementing actions or policies which undermine or threaten the territorial integrity, sovereignty and independence of Ukraine, as well as stability and security in Ukraine.
"It also shows that he is one of the leading businesspersons involved in economic sectors providing a substantial source of revenue to the government of Russia, which is responsible for annexation of Crimea and destabilization of Ukraine."
