Nico Rosberg looks to be the driver to beat in qualifying after posting the fastest time in final practice on Saturday at the Bahrain Grand Prix where security remains tight amid expectations of further anti-government protests.

Rosberg, who won the Chinese Grand Prix last week for his first Formula One victory, clocked 1 minute, 33.254 seconds in his Mercedes around the 5.4-kilometer (3.4-mile) Bahrain International Circuit. That was 0.147 seconds quicker than two-time world champion Sebastian Vettel and 0.409 seconds better than Vettel's Red Bull teammate Mark Webber.

McLaren's Lewis Hamilton, who was fastest in first practice, settled for fourth. Ferrari's troubles continued with Fernando Alonso finishing 10th and Felipe Massa 16th.

Pastor Maldonado of Williams was penalized five grid places for Sunday's race after needing a new gearbox.

He finished down in 11th in final practice as drivers struggled with tough conditions on the track, with temperatures reaching 43 degrees Celsius (109 degrees Fahrenheit) and winds whipping up sand from the surrounding desert. The heat on the track was especially hard on tires with several drivers wearing them down quicker than expected.

Security was tight following days of sometimes violent anti-government protests in Bahrain.

Bahrain authorities opened an investigation Saturday after the body of a man was found near the scene of Friday's clashes between protesters and security forces – in an area about 20 kilometres from the circuit.

Opposition groups claimed the man was killed by riot police in another possible blow to the Gulf nation as it struggles to quell unrest during the highly awaited return of the race after it had to be cancelled last year.

A statement by Bahrain's Interior Ministry said a probe was under way but the death nonetheless will likely intensify a wave of expected protests against the race later in the day.

There were checkpoints on the roads leading to the Bahrain International Circuit. Additional security troops have been deployed around the circuit and across the capital, Manama. But there were no signs of protests early Saturday anywhere near the circuit.

Demonstrators have called for the race to be canceled until the ruling Sunni dynasty enacts meaningful reforms aimed at addressing the concerns of the Shiite majority and ends its rights abuses.

Social media sites urged demonstrations as part of an opposition effort to use the worldwide spotlight on the race to press demands for a greater political voice. Bahrain's Shiite majority claims it faces widespread discrimination at the hands of the Western-backed Sunni monarchy.

At least 50 people have died in the unrest since February 2011.