By Yara Bayoumy DUBAI (Reuters) - The U.N. torture investigator said Bahrain had effectively cancelled a trip he had planned to the Gulf Arab state, where unrest led by majority Shi'ites against the Sunni ruling family has simmered for over two years. Juan Mendez, the U.N. Special Rapporteur on Torture, said in a statement it was the second time a scheduled visit had been postponed at short notice. His trip had been set for May 8-15.

Police clashed with Shiite demonstrators on Sunday only hours ahead of Bahrain's Formula One, but a massive security presence prevented any disruption to the race itself as Sebastian Vettel took the chequered flag. The Grand Prix was overshadowed by sometimes bloody clashes away from the circuit which dragged Formula One bosses into controversy for a second year in a row.

Bahraini police clashed on Sunday with Shiite demonstrators, only hours ahead of the Gulf state's Formula One Grand Prix race, which the authorities insisted would go ahead without disruption. Nico Rosberg of Mercedes will start on pole after outpacing fellow German and championship leader Sebastian Vettel of Red Bull in qualifying on Saturday. Spain's Fernando Alonso of Ferrari is third on the grid. But the racing has been overshadowed by sometimes bloody clashes away from the circuit which have dragged Formula One bosses into controversy for a second year in a row.

Bahraini protesters blocked roads and clashed with police at dawn on Sunday, only hours ahead of the Gulf state's Formula One Grand Prix, but the authorities said the race would go ahead without incident. Masked youths demonstrating against the staging of the race set alight tyres on roads in villages populated by Shiite Muslims just outside Manama, according to witnesses. But access was still open to the Sakhir circuit, south of the Bahraini capital.