Russia's Northern Fleet said in a statement released to the RIA Novosti government news agency that its four vessels were led by the Severomorsk destroyer and the Alexander Otrakovsky amphibious landing ship.
It said the detachment had passed through the narrowest part of the channel between England and France at Pas-de-Calais and would begin a series of planned manoeuvres shortly.
The quoted statement said a storm had forced the detachment to take temporary shelter at the Bay of the River Seine off the northwestern coast of France.
Both British and French officials told AFP that such Russian naval detachments visit the region on a nearly-annual basis and that they usually do not extend their stay beyond a few days.
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But a NATO spokesman said the ships "are not exercising in the channel, as some Russian headlines would have us believe."
"Our information indicates that the ships are transiting and have been delayed by weather conditions," NATO spokesman Jay Janzen told AFP.