Aidi Yursal, Jakarta – Hundreds of Islamic hard-liners in Medan took to the streets on Tuesday evening, storming clubs and other establishments they deemed an affront to Muslims preparing to celebrate Idul Adha, the Day of Sacrifice.

Members of the Islamic Defenders Front (FPI) sent customers fleeing when they marched into cafes and bars in the predominantly Catholic North Sumatra capital.

"We strode into these places while chanting the takbiran [or overnight prayers] over some loudspeakers," said Abdul Muthalib Daulay, chairman of the FPI's Medan chapter. "We called on the owners of the establishments in question to respect the Muslims trying to observe Idul Adha."

The FPI, known for launching raids and fierce protests, "would never have used violence to shut the places down," Abdul said. "We just went there to remind the people not to tarnish the night before Idul Adha with any immoral acts," he said, adding that the FPI had deemed these places of entertainment as "dens of iniquity."

Abdul called his group "polite and humane" and said the protests, which began after sunset prayers and ended at midnight, prompted the establishments in Medan to shut down "spontaneously."

Police said they had monitored the mob's movements and that there were no reports of violence against the customers.

Abdul said the protest was justified since the police issued an advisory ahead of the festival – celebrated on Tuesday and Wednesday, due to varying dates given by Muslim organizations – for bars and cafes to stay closed on Tuesday night.

"I'm really proud of the way the police cooperated with us [by merely monitoring us] and I'd like to thank them for helping us in our mission," he said.

Muslims mark the annual feast, which begins after hajj pilgrims descend from Mount Arafat in Saudi Arabia, with animal sacrifices to feed the less fortunate.