MADRID (Reuters) - Tens of thousands of Spaniards have gathered in the southern coastal city of Algeciras to demand the departure of a stranded British nuclear submarine awaiting repairs in Gibraltar, local media reported.

Carrying placards reading "Get the nuclear sub out" and "For our future," and headed by the leader of the Socialist regional government, the crowds marched through the centre of the city on Saturday to call for HMS Tireless to return to Britain for repairs.

The presence of the vessel, moored in the British colony since last May after it developed a leak in the cooling system of its nuclear reactor, has angered local residents who say it is dangerous. The British government says moving the vessel would be too risky.

Both the Spanish and British authorities have assured the public that the submarine poses no danger and that repairs are due to start soon.