Some of Wednesday’s female protesters tore off their shirts as they faced off with riot police carrying batons and shields.
Hun Sen said Tuesday he would take back land concessions if the violence continues.
Nearly 80 land cases involved government land concessions that affected more than 30,000 families.
Sia Phearum told “Hello VOA” people are being forced off land they earned through “backbreaking” work.
Nearly 400 families were forcibly evicted from the Borei Keila site this month.
Provincial Police Chief Chhoung Seanghak said police are working the case and focusing on the two guards.
The Documentation Center has collected nearly 1 million documents on the Khmer Rouge since 1995.
Cambodia is pushing for a seat on the council, UN Security Council, for 2013 and 2014; voting will be held later this year.
HRW also detailed what it views as severe violations of human rights in nations including Cambodia, Indonesia, Malaysia and Vietnam.
Phan Imex was supposed to build 10 buildings to house evicted residents and built eight instead.
Witnesses said security guards for the TTY Company opened fire with AK-47s.
Escapees climbed over the walls or jumped the metal gates of the Prey Speu Social Affairs Center Wednesday in full view of observers.