Britain and its NATO allies must defend deep sea cables against a potentially catastrophic attack by the Russia navy that could disrupt trillions of dollars in financial transactions, the head of Britain's armed forces warned.

The cables which crisscross the world's oceans and seas carry 95% of communications and over $10 trillion in daily transactions.

"There is a new risk to our way of life, which is the vulnerability of the cables that criss-cross the seabeds," the BBC quoted Stuart Peach, chief of the defence staff, as saying.

Peach said the Russian President Vladimir Putin's modernisation of the once mighty Soviet navy now posed a serious threat to Western communications.

"Russia in addition to new ships and submarines continues to perfect both unconventional capabilities and information warfare," Peach said.

Russia has repeatedly dismissed Western concerns about its renewed assertiveness as Cold War hysteria, though Kremlin supporters praise Putin at home for putting restoring Russia's clout after the 1991 collapse of the Soviet Union.