During this first phase of registration, 1,000 of the 6,500 Maoist soldiers in the camp will have their weapons verified, Buddha said.
As part of the peace deal that saw 83 Maoist MPs sworn into the country’s new interim parliament alongside mainstream politicians earlier this week, the former rebels will keep a key to the locked-up weapons.
The army is expected to submit a similar number of weapons for storage.
The media were not allowed to observe the procedure at the camp around 200Km southwest of the Nepalese capital Kathmandu.
Over 100 ex-Gurkha soldiers will be monitoring the 28 camps in seven different areas before the full UN contingent arrives.
The UN plans to send up to 186 monitors to help enforce the peace pact, and to deploy officials to help with the assembly elections, expected to be held in June.
The Maoists claim to have 35,000 soldiers in their "People's Liberation Army," but independent estimates put their numbers at closer to 12,000.
The UN official pointed out that "it is not surrender of weapons, it's the Maoists storing the weapons in UN containers."