Activist Tep Vanny, arrested with other demonstrators attempting a protest Monday, is taken away by Phnom Penh security forces. She and others were later released. Getty Images
PHNOM PENH, Cambodia—Police briefly detained five activists Monday as they tried to deliver a petition to French diplomats in Phnom Penh, where a ban on protests took effect Saturday.
The five women—land-rights advocates who have campaigned against the reclamation and development of a lake in Phnom Penh—were planning to ask the French embassy for help in securing the release of other activists who were recently detained, rights groups said. It isn't clear why they sought French officials for help.
Police released the women a few hours later, after holding them for questioning in a Phnom Penh police station.
After her release, Tep Vanny, one of the arrested, told reporters that police had initially accused them of flouting the ban on public assembly and protests. "We told them that we weren't demonstrating, and only intended to deliver a petition to the French embassy," she said. "The authorities then told us not to hold any demonstrations for the time being."
The other four arrested were Yorm Bopha, Pan Chunreth, Bop Chorvy and Sok Srey Leap, according to the Cambodian League for the Promotion and Defense of Human Rights, also known as Licadho.
Military police spokesman Brig. Gen. Kheng Tito confirmed the activists' arrests and subsequent release, but didn't give reasons for the actions. French embassy officials weren't immediately available to comment.
Cambodian authorities, facing growing political unrest, have cracked down on opposition and labor protesters in recent days. Police shot and killed at least four people at a labor protest Friday, and on Saturday security forces cleared out opposition supporters from their main rallying point in Phnom Penh. The government also banned protests in the capital indefinitely, citing public-order concerns.
At least 23 other people were arrested during the weekend crackdown, and these detainees have been kept out of reach of their families, lawyers and medical professionals, according to Licadho. A police official confirmed that arrests had been made, but declined to verify the number.
Ms. Vanny and Ms. Bopha are leading representatives of a group of residents who oppose the development of Boeung Kak Lake in northern Phnom Penh. The project, which started in 2007, resulted in the eviction of thousands of people, many of whom resisted resettlement partly due to what they say was unsatisfactory compensation.
—Sun Narin contributed to this article.
Write to Chun Han Wong at chunhan.wong@wsj.com