PHNOM PENH – Cambodian riot police broke up a rally Sunday arresting an activist, an official said, in the latest move by authorities to quell protests against Prime Minister Hun Sen.

About 50 security officers, armed with batons, dispersed a small group of around 10 people as they tried to hold prayers in the capital Phnom Penh for the release of people arrested during a recent bloody crackdown, Am Sam Ath, of local rights group LICADHO, told AFP.

The acting leader of a non-governmental organisation was dragged into a police car, he said, adding there "was no violence" as the prayer group did not resist.

Long Dimanche, a spokesman for the Phnom Penh city hall, confirmed police had dispersed the group because they had held a rally deemed to violate the law.

"They held a public rally without permission (from authorities) and disturb the order... This is a yellow card for those who do not respect the law," he told AFP.

He said the detained activist would be soon released.

Earlier this month police opened fire on striking garment factory employees demanding a minimum wage of $160 per month for their work in an industry which supplies brands including Gap, Nike and H&M, killing at least four civilians.

Police also arrested at least 23 people.

The government says the recent rallies were illegal and has indefinitely banned opposition demonstrations in the capital.

Hun Sen, who has ruled for nearly three decades, has faced accusations of excessive force against striking garment factory workers seeking higher wages as well as opposition demonstrators who allege vote-rigging in elections last July and call for Hun Sen to resign.

The opposition Cambodia National Rescue Party has boycotted parliament since the July polls.

Hun Sen reiterated last week that he would not resign, and told the opposition party to wait for the next election in five years' time.

The 61-year-old premier  has vowed to stay in power until he is 74.