Stora Enso has confirmed that 2,000m³ of its sawn timber was on board a ship which has gone missing off the coast of Portugal.

The disappearance is becoming more mysterious after it was revealed that the Russian-manned vessel, The Arctic Sea, was boarded by unknown masked assailants days earlier in Swedish waters.

Stora Enso said its timber on the Arctic Sea, destined for the Algerian construction trade, had been worth about €300,000. It said the cargo was fully insured and Stora Enso had no risk exposure. The rest of the timber on board was believed to have come from a variety of other sawmillers.

The Arctic Sea, with 12 crew aboard, originally set sail from the Finnish port of Pietarsaari and was then attacked briefly near the Swedish island of Oland in the Baltic Sea. The attackers searched the vessel and then left.

Russian maritime journal Sovfracht said Russia’s Maritime Safety Service, navy and the Federal Security Service are investigating the matter. The last known position on July 29 was off Portugal.

The timber consignment was destined for arrival in Algeria on about August 4.