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
ITV News has uncovered claims that some anti-poaching rangers working in a UK aid-backed project were complicit in elephants' slaughter.
There are multiple "injuries and casualties" after a carriage fell off the bridge and into a highway near the US city.
She rejected comments from the chief EU negotiator who said there was "no way" the UK could "cherry pick" elements of a trade deal.