Out of an estimated total of 1,082,000 personnel on active duty in 2000, 950,000 were in the army, 46,000 in the navy, and 86,000 in the air force. An additional 4.7 million were in the reserves, and there was a civilian militia of 3.5 million. Equipment includes some 3,500 main battle tanks, 26 submarines, and 620 combat aircraft. The DPRK has admitted to developing a nuclear weapons program. North Korea provides advisors to 12 African countries. The Ministry of Public Security controls 189,000 internal security forces. Defense expenditures in 2001 totaled an estimated $5.1 billion or 31% of GDP. Because of the secrecy inherent in the DPRK, reliability of the figures provided is uncertain, as is information on the combat readiness of its forces.