SAN JOSÉ (AFP) - A catamaran carrying 98 tourists and 10 crew members sank off Costa Rica on Thursday, leaving at least four people dead while rescuers saved dozens from the sea.

Rescuers have plucked 94 people from the Pacific waters so far, fire brigade director Hector Chaves told Radio Monumental.

The identities of the victims have not been disclosed so far.

Survivors "are being treated by medical personnel. Many have problems like hypothermia and panic attacks," Mr Chaves said.

The ship began to sink after it was slammed by a huge wave, said public security deputy minister Maria Fulmen.

"Five boats have been deployed to the area with everything they need for the rescue, as well as two helicopters to rescue people and take them to hospitals," Ms Fulmen said.

The catamaran had sailed off from Los Suenos on the Pacific coast and was heading to Tortuga Island when the shipwreck happened some 15km offshore.

Costa Rica has been hit by powerful winds that have produced huge waves, while tearing down trees and billboards inland.

The transport ministry said the catamaran was a 2007 model and was authorised to carry 120 passengers and 10 crew members.

The ship appeared to have enough lifeboats and life jackets, according to the ministry statement.