NATO has sent Dutch warship HNLMS Rotterdam to the Baltic Sea, Finnish public broadcaster YLE reported on Monday.
The ship is south of Bornholm, a Danish island, YLE said, citing Finnish and Swedish media.
"It's a planned position and they're there to show presence and solidarity with the whole alliance," a NATO spokesperson told newspaper Aftonbladet.
Last week three Russian landing vessels sailed into the Baltic Sea via the Danish strait. Non-NATO member Sweden responded to the move last Friday by reinforcing its military presence on the island of Gotland in the Baltic Sea.
The moves come as Russia masses approximately 100,000 troops on Ukraine's borders, raising tensions in the region. Experts believe Russia could be planning to further invade the country.
A week of meetings between Russia, the U.S., NATO and the OSCE took place last week but ended with no clear way forward or plans for deescalation.
Other NATO members are also taking action.
Denmark will also send a frigate with a 160-strong crew to patrol the Baltic Sea later this month and four additional fighter planes to Lithuania.
Denmark is responding to Russia's actions on the Ukrainian border by strengthening its defense capabilities in the Baltic Sea, the Danish ambassador to Estonia said last week.
On Monday, Latvian Defense Minister Artis Pabriks told Latvian Television the country would step up its military presence in the eastern regions of Vidzeme and Latgale.
Editor: Helen Wright