|Force India pulled out of the second practice after four of their mechanics were caught up in clashes between security officials and protesters on Wednesday [GETTY]
Nico Rosberg topped the times for Mercedes in Friday's second free practice session ahead of this weekend's controversial Bahrain Grand Prix after the Force India team had chosen to withdraw early on safety grounds.
The 26-year-old German followed up his maiden Formula One victory in last weekend's Chinese Grand Prix at Shanghai with a controlled demonstration of his potential and the speed of his Mercedes car.
On a tense day with intensified security around the Sakhir circuit, Rosberg produced a measured performance to clock the best lap midway through the 90-minutes' action in one minute and 32.816 seconds.
This lap time left him four-tenths of a second clear of nearest rival Australian Mark Webber of Red Bull who, in turn, was ahead of his team-mate defending champion Sebastian Vettel of Germany.
World championship leader Briton Lewis Hamilton of McLaren, who topped the times in the morning's opening free practice session, was unable to repeat his pace and struggled to fourth with a revised set-up as the track temperature fell from 40 degrees Celsius to 33 degrees.
The Force India team chose to take no part in the second session, instead preparing their cars for Saturday's running - having used their allocation of soft tyres in the morning - in order to make an early departure to their hotel before nightfall.
Four of the team's mechanics had been caught up in a confrontation between police and protesters on the highway back to the capital city Manama on Wednesday evening when a petrol bomb exploded close to their unbranded rental car.
Two members of the Silverstone-based team reacted to the incident by asking to leave and they flew home on Thursday.
The Sauber team on Friday also issued a statement that confirmed they drove through a similar incident on Thursday evening. None of the 12 mechanics in the unmarked mini-bus were hurt.
Seven-times champion German Michael Schumacher, 43, was fifth in the second Mercedes ahead of Hamilton's McLaren team-mate and compatriot Jenson Button, Japanese Kamui Kobayash of Sauber and two-time champion Spaniard Fernando Alonso of Ferrari.
Frenchman Romain Grosjean was ninth for Lotus and Mexican Sergio Perez of Sauber wound up 10th.