The Indonesian economy expanded at the slowest pace in six years in 2015, the official Central Statistics Agency said on Friday.

However, Indonesia's $800 billion economy, the biggest in Southeast Asia, picked up speed in the fourth quarter.

While the full-year growth was 4.79 percent in 2015, Gross Domestic Product expanded 5.04 percent in the October-December quarter from a year earlier.

The slowest annual expansion since the global financial crisis of 2009 followed a collapse in prices for its main commodities and the slowing down of major trading partner China.

The pick-up in quarterly growth above 5 percent was a result of higher public spending and beat analyst expectations of 4.80 percent growth.

The upbeat quarterly figures pointed at the increasing success of President Joko Widodo in re-booting the economy.

Widodo rolled out a series of stimulus measures in September last year in an attempt to make investment, especially in manufacturing, the main driver of growth, according to Reuters.

"The government appears to have found better footing by now and infrastructure projects would start to help momentum more forcefully," said Wellian Wiranto, an economist with OCBC in Singapore, the agency reported.

Indonesia's central bank cut its benchmark interest rate by 25 basis points to 7.25 percent, the first time it revised rates in 11 months, to boost growth.