A rights advocacy group in Cambodia says police have detained eight activists, including two Westerners, who were staging a peaceful protest in support of human rights workers who were jailed last week.

Om Sam Ath of the group Licadho said the eight were among as many as 200 people demonstrating Monday to show their solidarity with one former and four current officers of another human rights group, ADHOC. He said the two Westerners were German and Swedish, and worked as advisers to Licadho.

The marchers were wearing black clothing for their campaign supporting the five people jailed last week, who are accused of conspiring to bribe a woman to deny that she had an affair with an opposition leader.

The government warned Sunday that the protest would be considered illegal.