Chalerm Yubamrung, director of the Centre for Maintaining Peace and Order (CMPO), made the claim on Friday as police began efforts to reclaim some rally sites.
Mr Chalerm claimed that police found ping-pong bombs, knives, slingshots, explosive devices and drugs at the protest base on Ratchadamnoen Nok Avenue after they successfully reclaimed the area that protesters had occupied since early November.
Mr Chalerm displayed the illegal items at a news conference.
Shortly afterward, Mr Suthep and other PDRC co-leaders asserted that the seized weapons and drugs did not belong to PDRC members.
They said that the area from the Suan Misakawan intersection to Makkhawan Rangsan Bridge was controlled by independent protest groups, not the PDRC or its allies.
Mr Suthep said the PDRC firmly adhered to the Buddhist principle of ahimsa or non-violence and engaged only in peaceful protests.
Post Today quoted a source from one of the groups managing the Nang Loeng intersection protest base that leaders agreed to allow riot police to take back the area between Suan Misakawan to Makkhawan Rangsan Bridge.
The source from the People's Democratic Force to Overthrow Thaksinism (Pefot) said the decision was made because the area was controlled by violence-prone vocational students who refused to obey instructions from Pefot, the Network of Students and People for Reform of Thailand (NSPRT) and the Dhamma Army.