Russia has deployed a reconnaissance ship to the eastern Mediterranean in a bid to "to gather current information in the area of the escalating conflict", a military source told Interfax news agency.
The ship is understood to have left the naval base in the Ukrainian Black Sea port of Sevastopol late on Sunday.
The Defence Ministry declined to comment on the reports.
More top news
Largely dry night, but showers set to spread in from the west during tomorrow.
Any lingering showers will ease, to leave a dry night with plenty of clear spells. Cloud thickening from the west, but staying dry.
Crowds of people gathered in Sandringham on Sunday to catch a glimpse of Princess Charlotte as she arrived for her official christening.