Dozens of Spanish fishing boats sailed to Gibraltar yesterday to demand that the British outpost remove 70 concrete blocks it has dropped in their fishing grounds. British naval and Gibraltar police patrols blocked the 38 Spanish boats from entering disputed waters around the concrete reef, which has sparked an angry diplomatic row between London and Madrid. In the midst of the spat, Britain's helicopter carrier HMS Illustrious visited a Spanish port yesterday and a frigate was scheduled to dock in Gibraltar today in pre-planned exercises. The Spanish fishermen from the nearby ports of La Linea de la Concepcion and Algeciras set sail on calm waters across the narrow strait, accompanied by a half dozen Spanish police patrols. The Spanish fleet approached a cordon set up by a total of 14 British naval and Gibraltar vessels, manoeuvring in close quarters but then turning back with no incident reported. About 500 people watched the one-hour protest from the shores of Gibraltar, many waving Gibraltar and British flags. Spanish spectators gathered in the port of La Linea de la Concepcion, some with Spanish flags and T-shirts reading "Gibraltar Is Spanish". "We just want to send a message to Gibraltar," said Leoncio Fernandez, the head of the La Linea fishermen's guild. "All we want is to fish where we have always fished." Gibraltar police said their main concern was safety. "When you're working at sea in such close quarters, it can be very dangerous," a spokesman said. The Gibraltar government says the reef will regenerate marine life and that the few Spanish fishermen who raked there for shellfish did so illegally. Spanish fishermen, however, say the blocks - dropped into the sea last month without consultation - have cut them off from rich fishing grounds. Agence France-Presse