THE Royal Navy has sent a ship to help with the hunt for a lost Argentinian navy submarine with 44 crew on board.

Argentina's navy said communications with the ARA San Juan were lost on Wednesday when it was returning to its base at Mar del Plata, south of Buenos Aires, after a routine mission to Ushuaia, near the southern-most tip of South America.

Admiral Gabriel Gonzalez, chief of the Mar del Plata base, said the sub had sufficient food and oxygen but fears are growing after scans of radio transmission frequencies failed to locate the vessel.

Relatives of some of the crew members are at the base. “We are praying to God and asking that all Argentines help us to pray that they keep navigating and that they can be found,” said Claudio Rodriguez, brother of one of the crew members. “We have faith that it's only a loss of communications.”

An Argentine destroyer and two corvettes are conducting a search around the area of the sub's last known position off the south-eastern Valdez peninsula.

The Royal Navy has deployed an ice patrol ship to help with the hunt. A spokesman said: “Following a request from the Argentine government, HMS Protector has been deployed to join the search and rescue effort for the ARA San Juan.”

Argentinian navy spokesman said heavy winds and high waves are hampering efforts.

“Detection has been difficult despite the quantity of boats and aircraft" involved in the search, he said. “We are investigating the reasons for the lack of communication. If there was a communication problem, the boat would have to come to the surface.”