The Russian navy reportedly claims to have driven away a submarine, believed to be American, that entered its waters.
The Northern Fleet apparently sent several vessels and an anti-submarine Il-38 aircraft to persuade what was thought to be a Virginia class fast attack sub to leave.
No force was used in the operation and a naval official said contact with the vessel lasted 27 minutes.
The incident comes amid heightened tensions between the West and Russia over Moscow’s role in the Ukraine conflict.
Russian state news agencies cited an unnamed representative of the navy’s general staff as saying the incident happened on Thursday in the Barents Sea in its northern waters.
Thanks to “active measures by the Northern Fleet’s anti-submarine forces, the submarine was ‘pushed away’”, the official was quoted as saying.
The deputy head of the Russian parliament’s foreign affairs committee, Leonid Kalashnikov, said such incidents are quite common.
He told Echo of Moscow radio: “Occasionally other countries test how the submarine location service is working.”
The Barents Sea lies off northwest Russia and the Northern Fleet is based on its shores.