Denmark and Lithuania have become the latest Baltic navies to buy Finland's Blocker naval mines, signing up to a five-nation joint procurement programme aimed at strengthening maritime defences in the Baltic Sea.

Denmark's Defence Acquisition and Logistics Organisation, known as FMI, signed an agreement to procure the Blocker system from Finnish manufacturer Forcit Defence, the Danish defence ministry announced on 5 November. Lithuania decided to go ahead with its own contract a day earlier.

The purchases are being made through the Naval Mines Cooperation, a multinational programme led by Finland that was launched in 2024 and developed through a framework agreement in 2025. Finland, Denmark, Lithuania, Germany and Norway are taking part in the initial joint procurement, although Germany and Norway have not yet publicly announced contracts of their own.

The Finnish military signed a contract with Forcit Defence in June on behalf of the five participating countries. The Finnish government said the deal was worth hundreds of millions of euros, although the press releases did not say how many mines Denmark is buying or what the Danish share of the cost will be.

Blocker is a seabed influence mine that detects passing ships through their physical signatures rather than needing contact with a hull. Forcit advertises the weapon as having an explosive effect equivalent to more than 1,000 kilograms of TNT.

Finland and Estonia already operate the system. Estonia bought Blocker mines in 2021, making it the first foreign customer for the Finnish weapon.

Commander Steen Balslev, head of the Maritime Division at FMI, said the purchase would strengthen Denmark's ability to defend its waters and to operate alongside its allies.

With the procurement of BLOCKER, we are strengthening Denmark's maritime defense and our ability to carry out missions together with our allies, Balslev said. Through international cooperation, we can jointly procure an important capability while also strengthening cooperation on equipment and operational requirements across the participating countries.

The Danish ministry said the mines are mainly intended to be deployed from new mine-laying vessels, which are scheduled to be ready as the transition to 2029 takes place.

Beyond the joint purchase, the Naval Mines Cooperation is meant to deepen collaboration on logistics, training, exercises and the service life of the systems, the Danish ministry said.

Ten countries signed the programme's original declaration of intent: Belgium, Latvia, Lithuania, Norway, Poland, Sweden, Denmark, Germany, Finland and Estonia, all of them members of NATO.

The deal reflects a renewed European investment in naval mine warfare. The Baltic Sea has become a focal point of tension since 2022, when Russia launched its full-scale invasion of Ukraine. With Finland and Sweden now in NATO, the sea is almost entirely surrounded by alliance members, apart from Russia's Kaliningrad and Leningrad coasts.

Russian ships must pass through the narrow Danish straits and on through the Kattegat and Skagerrak to reach the open ocean, which makes control of those waters a strategic priority for Copenhagen and its allies.

Naval mines have also returned to the headlines this year, with Iran using the weapon to threaten shipping through the Strait of Hormuz during the conflict with the United States and Israel.

Germany may still announce its own procurement decision before the end of the year, according to German defence industry publication Hartpunkt, citing well-informed sources. For now, Denmark and Lithuania are the first of the five partners to move from the joint framework to signed contracts.