STOCKHOLM (AP) -- Sweden said Saturday it will step up insurance checks on foreign ships in a move aimed at tightening controls on Russia's so-called "shadow fleet " of aging ships.

The government in Stockholm said that, starting July 1, the coast guard and the Swedish Maritime Administration will be tasked with collecting insurance information not just from ships that call at Swedish ports, but also those that pass through the country's territorial waters and exclusive economic zone.

"This underlines Sweden's clear presence in the Baltic Sea, which in itself has a deterrent effect," Prime Minister Ulf Kristersson said in a statement. "It also provides Sweden and our allies with important information about vessels that can be used as a basis for sanctions listings of more vessels in the shadow fleet."

Russia uses its shadow fleet to transport oil and gas, or to carry stolen Ukrainian grain. The European Union has now targeted almost 350 of the ships in total in sanctions packages, most recently on May 20.

Kristersson said that "we are seeing more and more problematic events in the Baltic Sea and this requires us not only to hope for the best, but also to plan for the worst."

The average age of the vessels is around 18 years, meaning they're near the end of their lifespan and are more vulnerable to accidents, especially if they're not well-maintained.