Seventeen members of a Cambodian rights group and environmental NGO were briefly detained by authorities in Cambodia's southeastern Koh Kong province Wednesday as they observed protests calling for the release of three activists held for interfering with sand-dredging operations, sources said. The 17 activists from the rights groups Licadho and Adhoc and environmental advocacy group Mother Nature were taken into custody in the afternoon and questioned on their role in the protests, which are now entering their third week. They were released without charge at around 6:00 p.m. Though the 17 were initially accused of taking part in the demonstration, the activists had come only to monitor the protest, Adhoc provincial official Nheab Samoeurn told RFA's Khmer Service on Wednesday. "We have video clips and other evidence showing that we didn't join with the demonstrators, but only stood close by so that we could take pictures," he said. Licadho provincial coordinator In Kongchit, who was among those detained, said the rights group was present on Wednesday to observe two separate protests outside the provincial court. The police officers who took them into custody had abused the law, he said. "The authorities have used excessive force and the court system itself to crack down on rights groups," In Kongchit said. "They have interfered with our right to do our work," he said. Pressure to sign Am Sam Ath, a senior investigator for Licadho who traveled to Koh Kong after the 17 were detained, said that police had attempted to pressure the group to sign a "contract" promising to seek permission from authorities before monitoring future protests. They were also told to stay away from the protests themselves and not take part, he said. "But the group refused to sign any contracts," he said, adding that the police finally decided to release them anyway. "It is a serious human rights violation to ask rights groups to "sign contracts,' and it is against the law," Am Sam Ath said. "Our job is to monitor demonstrations, protests, and other events to witness and make note of any rights violations." "This is our role, which is guaranteed by the[Cambodian] constitution and the U.N.," he said.