North Korea's actual military spending is believed to be about 15 times the announced amount in 2009 as the communist regime continues to build up its military capacity despite the country's moribund economy, a South Korean defense research institute said Tuesday.

The North said it spent US$570 million on its military in 2009, but the real expenditure, calculated on an exchange rate based on purchasing power parity terms, was $8.77 billion, the state-run Korea Institute of Defense Analyses (KIDA) said in a report.

"In spite of its economy shrinking since the mid-2000s, North Korea has gradually increased its military spending," the report said.

North Korea maintains the world's fifth-largest army with an active duty military force of 1.19 million, compared to about 655,000 in the South.

According to figures released by North Korea, its military spending rose to $570 million in 2009 from $540 million in 2008, $510 million in 2007 and $470 million in 2006, the KIDA said.

As of 2009, North Korea's gross national income stood at 28.6 trillion won ($25 billion), compared with the South's 1,068 trillion won, the KIDA said. 

(Yonhap News)