The Defence Forces has said it is monitoring two Russian ships off the west coast of Ireland.
The ships were involved in the construction of the Nord Stream 2 pipeline.
They have returned to Irish waters, despite appearing to depart towards Africa earlier this week.
The Defence Forces has said both the Air Corps and the Naval Service are aware of the vessels, but it will not be releasing any further information on the operation.
"Both continue to monitor activity in Irish waters and to undertake Maritime Defence and Security Operations (MDSO) throughout Ireland's maritime domain," a statement said.
Independent Senator and Security Analyst Tom Clonan said these ships are well-known to the defence community.
"One of them has a diving platform and in its equipment it has deep-sea submersibles," he said.
'Potentially a risk'
Senator Clonan said this ability, and their location off the south-west coast "is potentially a risk to our subsea oceanic cables."
"These are the fibre optic transatlantic cables that come from Ireland [and] basically connect the European Union to the United States.
"Something like one-third of all of the data online goes through these cables, so they're a really, really critical piece of infrastructure".
Senator Clonan said we should be 'very mindful' of the presence of these ships.
"We know that the Russians have targeted such fibre optic cables in the Black Sea, for example, prior to their invasion of Ukraine.
"So we need to be very, very mindful of their presence in our territorial waters".
Senator Clonan said the Russian ships can be there under freedom of movement in international waters, "but the fact that they're in that area off our coast, where all that critical infrastructure is, is a threat.
"Unfortunately we don't have the naval vessels to go out and shadow them."
Senator Clonan said this is also "of great concern to our European Union partners, and our United States partners.
"This critical piece of infrastructure links the United States with the European Union; and unfortunately Ireland is Europe's weakest link when it comes to defence and intelligence infrastructure," he added.
Additional reporting: Ellen Butler