Dutch customs officials have added six more yachts to their list of boats which cannot leave the country, taking the total tied up because of the sanctions against Russia to 20.

Fourteen of the yachts are under construction, four are being built and two are in winter storage, the customs department said. Two of the yachts on the list are over 100 metres long.

So far officials have identified a link between people on the sanctions list and a boat in just two cases. Three ownership structures are still being investigated. The other 15 have no links to Russians on the sanctions list but remain impounded because of the export ban.

The two boats with links to the sanctions list are both 8.5 metres long and belong to a superyacht, the customs department said, without giving further details. Both are in the Netherlands for maintenance.

None of the boats can be handed over to their owners but they are allowed to make ‘test drives’ within a limited, pre-determined area and under full surveillance, customs officials said.

Last weekend it emerged that a Dutch-built yacht belonging to sanctioned Russian billionaire Roman Abramovich was offloaded on the first day of the invasion of Ukraine.

The Guardian reported that the vessel, which is currently sitting in dry dock in Vlissingen, was transferred to David Davidovich, a ‘close associate’ of the former Chelsea owner.

The 50m-long four-deck Aquamarine was built by Oss-based Heesen Yachts and finished in January 2021, with a reported price tag of €33 million.