Formula One leader Lewis Hamilton stalled his Mercedes early in the session after misjudging the entry into a turn. The British driver drove solidly after that, finishing a fraction of a second behind Raikkonen’s Ferrari under floodlights at the 5-kilometer (3.1-mile) Marina Bay track.
Max Verstappen was .5 seconds behind Hamilton in third, with Red Bull teammate Daniel Ricciardo fourth.
Sebastian Vettel was nearly two seconds behind Raikkonen in ninth, but set the time on slower tires than his teammate. He could not get onto the quicker tires after clipping a wall and damaging the rear right corner of his car. It forced the German driver back to the team garage, although the extent of the damage was not immediately clear.
It was hardly ideal preparation for Vettel, who has looked out of form in recent races. He is second in the overall standings and trails Hamilton by 30 points with six races remaining after Singapore.
Both drivers are aiming for a fifth F1 title.
Earlier, Ricciardo was quickest in the first practice ahead of Verstappen, with Vettel in third ahead of Raikkonen.
In the first session, Hamilton had a scary moment when his front wheels locked and he momentarily veered off the track. Also, Sauber driver Charles Leclerc, who is replacing Raikkonen at Ferrari next year, mangled his front right suspension after clipping the barriers.
There is a final practice Saturday evening before qualifying at 9 p.m. local time.
By JEROME PUGMIRE, Associated Press