A lifeboat from a British-operated cruise ship has fallen into the sea at port in Spain's Canary Islands during an emergency drill, killing five people and injuring three others.

Thomson Cruises issued a statement saying it "is aware of an incident involving the ship's crew on board Thomson Majesty in La Palma."

"We are working closely with the ship owners and managers, Louis Cruises, to determine exactly what has happened and provide assistance to those affected by the incident," the statement added.

Rescue personnel were called to the dockside at midday after "a lifeboat with occupants had fallen overboard from a cruise ship docked at the pier of Santa Cruz port in La Palma," a regional government statement said.

Widespread reports in Spanish media said the crew was conducting an emergency drill at the time of the accident.

Television images showed a small, white two-hulled lifeboat capsized beside the ship. It was not immediately clear whether the Thomson Majesty ship had any passengers on it.

The nationality or sex of those who died wasn't immediately known, the regional government statement said, adding that the injured were all men, two aged 30 and another, a Greek national, was 32 years old.

The injuries weren't considered to be life-threatening, it said.