Some of the weapons have fallen into the hands of armed groups operating in the east of the country, warns the confidential report by UN experts that was obtained by AFP on Thursday.

The Democratic Republic of Congo's east is one of Africa's flashpoints, gripped by militia violence that has claimed more than 1,000 lives in a matter of months and caused more than half a million people to flee their homes.

The government in Kinshasa has in the past accused neighboring countries of seeking to destabilize it. These governments have in turn said that DR Congo, a vast country the size of western continental Europe, is a haven for groups that oppose them.

The UN experts are monitoring sanctions against the country that expire at the end of June.

The experts point to instructors and equipment from Albania, Romania, Turkey, South Africa, Israel, China, Iran, the United Kingdom, North Korea, Sudan and the United States, among others.

DR Congo and its military have not been subject to an arms embargo since 2008, though one still applies to armed groups.

However, the training of the military or delivery of arms to them remains subject to notification.

UN sanctions may also include travel bans and asset freezes.

The report noted that several countries "delivered significant quantities of arms, ammunition, equipment and military vehicles" to the military.

That included civilian helicopters transferred for military use, the report says.

"Over the last decade, a large part of the air logistics of FARDC (the military) relied on a fleet of foreign civilian-registered cargo carriers operating in contravention of international and national civil aviation norms and regulations," it states.

"Some of the material delivered to FARDC was later diverted to armed groups in eastern" DR Congo, the report continues.

Chinese authorities have said they are investigating the claims, while Iran denied it had ever transferred any material to the DR Congo, igniting fears the equipment had been sent by a third party.