The head of Sweden's armed forces says the country will station permanent troops on the strategic island of Gotland amid increasing tensions in the Baltic Sea region.

Supreme Commander Micael Byden says troops currently training on the island will remain there with immediate effect, six months earlier than planned for a full unit to replace them.

Byden told national broadcaster SVT on Wednesday that "the situation in the region has deteriorated over time" and that the forces "are demonstrating responsibility for the country's sovereignty with an increased military capability."

Defense Minister Peter Hultqvist described the decision as sending a signal about Sweden's awareness of the security situation in light of Russia's annexation of Crimea and "increasing pressure" on the Baltic states of Estonia, Latvia and Lithuania.