Hundreds of protesters led by the People's Democratic Reform Committee besieged the Office of the Permanent Secretary for Defence Ministry Monday to force the caretaker government from using it as an office.
Initially, some 500 protesters led by Chumpol Julasai, Natthapol Thipasuwan and Sokonthee Phatthiyakul arrived at the office at noon.
Troops guarding the office set up three layers of barbwires to prevent protesters from storming inside.
Leaders of the protesters demanded that Gen Niphat Thonglek stop allowing caretaker Prime Minister Yingluck Shinawatra to use the office as her temporary office.
At noon, Phutthipong Puttipong Punnakan led several hundreds more of protesters and state enterprise unionists to join the rally.