LEADERS around the Baltic Sea reacted warily today to reports that Russia could revise the borders of its territorial waters in the region.

In a draft proposal reported by some Russian media, Russia’s Defence Ministry suggests updating the co-ordinates used to measure the strip of territorial waters off its mainland coast and that of its islands in the Baltic Sea.

The existing co-ordinates were approved in 1985, the ministry says; saying, they were “based on small-scale nautical navigation maps” and do not correspond to the “modern geographical situation.”

It was not immediately clear from the draft whether the proposed changes would shift the border or merely clarify it.

Swedish Prime Minister Ulf Kristersson said that Russia had signed a United Nations convention that regulates how to make such changes.

“Both we and Finland assume that Russia — which is a signatory party to that convention — lives up to that responsibility,” he said.

If Russians were to challenge borders, “then Russia violates a UN convention, then Russia has the whole world against it,” Finland’s Foreign Minister Elina Valtonen said.

She said, however, it was likely a routine act by Russia and not a provocation.

Finnish President Alexander Stubb wrote on Twitter that Russia had not been in contact with Finland on the matter. “Finland acts as always: calmly and based on facts,” he wrote.

Lithuanian Foreign Minister Gabrielius Landsbergis asserted that Russia was “attempting to spread fear, uncertainty and doubt about their intentions in the Baltic Sea.”

The Baltic News Service said that Lithuania summoned the Russian representative for a detailed explanation today.

However, Russia’s Interfax news agency cited an unnamed military diplomatic source as saying Moscow does not intend to revise the border or the width of its territorial waters.

Kremlin spokesman Dmitry Peskov told reporters there was “nothing political” in the Defence Ministry’s proposal.

“You see how tensions and the level of confrontation are escalating, especially in the Baltic region. This requires appropriate steps from our relevant bodies to ensure our security,” Mr Peskov said.

Since Russia’s full-scale invasion of Ukraine in early 2022, Finland and Sweden have joined Nato.

The Baltic Sea — Russia’s maritime point of access to the city of St Petersburg and its Kaliningrad enclave — is now almost surrounded by members of the military alliance.

Kaliningrad is sandwiched between Lithuania to the north and east and Poland to the south. It is home to the Russian Navy’s Baltic Fleet.