The images, credited to the Estonian Coast Guard and posted by the Estonian weekly Eesti Ekspress and the Finnish daily Helsingin Sanomat, were described as the first documented evidence of a Russian civilian vessel in the Baltic Sea carrying a mounted heavy weapon.
The vessel, the floating LNG terminal Marshal Vasilevskiy, is operated by Russian gas giant Gazprom, Polish state news agency PAP reported.
According to Helsingin Sanomat, many members of the crew have military backgrounds, and some are officers of Russia's Federal Security Service (FSB).
Analysts cited by the outlets said the heavy armament was intended to deter NATO countries and increase the risks associated with any attempt by Western authorities to seize the vessel.
Finnish authorities have previously boarded Russian-linked ships in the Baltic, including a tanker believed to be part of Russia's so-called shadow fleet and a cargo vessel carrying Russian goods, during investigations into suspected damage to undersea cables.
Those operations were supported by Finnish military and special forces units.
(jh/gs)
Source: PAP