Customs officials have placed 14 yachts at five Dutch shipyards which are being built or repaired for wealthy Russians under ‘extra supervision’, finance minister Wopke Hoekstra has told MPs in a briefing.

The list is made up of 12 yachts under construction, including one of over 35 metres, and two which are undergoing maintenance, Hoekstra said.

The boats will not be allowed to leave the country because of the export ban and sanctions which have been imposed on hundreds of wealthy Russian supporters of president Vladimir Putin.

The ultimate ownership of the yachts is currently being researched, Hoekstra said.

Specialist magazine Superyacht Times said last month that Russian customers accounted for 9% of luxury yacht sales and 13% of boats longer than 40 metres.

Work has also started on investigating property ownership. The Dutch land registry office Kadaster has not so far identified any private individuals on the sanctions list with property in the Netherlands and is now looking further into the ownership constructions, Hoekstra said.

The Netherlands has been criticised for its slow start to enforcing sanctions. On Monday, former minister Stef Blok was given the job of coordinating the Dutch approach.

Over a month since Putin’s troops invaded Ukraine, the Netherlands has sequestered almost €516 million in Russian goods and contracts, most of which has come via banks and trust offices, Hoekstra said last week and repeated again on Tuesday.

A further €155 million in transactions has been halted. The new total is still well below the €80 bn in Russian assets which the Financieele Dagblad suggests are based in the Netherlands, of which €45 bn belongs to people on the sanctions list.