Indonesian President Joko Widodo and first lady Iriana Joko Widodo show their ink-stained fingers after casting their ballots during elections in Jakarta. Picture: Reuters/Edgar Su

Jakarta - Indonesian President Joko Widodo was 13 percentage points ahead on Wednesday in the race to lead the world's third-largest democracy, based on 51 percent of votes counted, an unofficial early count of votes by pollster CSIS showed.

Widodo is running against former military general Prabowo Subianto after a six-month campaign dominated by economic issues and the rising influence of political Islam.

The incumbent had 56.7 percent of votes, while Prabowo had 43.3 percent, the Centre for Strategic and International Studies (CSIS) said.

CSIS is one of more than 40 groups accredited by Indonesia's election panel to conduct unofficial quick counts, based on samples from polling stations nationwide. Such counts by reputable companies have proved accurate in previous elections.

Tens of millions of Indonesians voted on Wednesday in the world's biggest one-day election to choose a president and representatives to national and regional level legislative assemblies. 

Reuters