Muslim militants in Indonesia's capital have vandalised a cafe in an area popular with foreigners because it was serving beer during the Islamic fasting month of Ramadan.

Around 300 members of the Islamic Defenders Front ordered customers at the Star Deli in south Jakarta to leave, before smashing the building's windows and doors, said Alawi Usman, a spokesman for the group.

"We are against immorality," he said. "The guys saw the beer on the table and what happened, happened. We are doing this for the future of the country's youth." No one was injured in the attack, which police did nothing to stop, Usman said. Police confirmed the raid occurred, but declined say why they did not try to prevent it.

Indonesia is the world's most populous Muslim nation, but its government is secular. It has significant Christian, Buddhist and Hindu populations. Islamic militancy has risen in recent years, and al-Qaida-linked terrorists have carried out three bloody attacks, including the 2002 Bali nightclub bombings.

The Islamic Defenders Front was formed in 2000. It has a history of vandalising entertainment centres during Ramadan. Many analysts say that extorting money from frightened bar owners – not Islamic principles – is its primary motive.

Star Deli is in Kemang, an area known for its restaurants, cafes and bars. It is popular with foreigners and wealthy Indonesians.

The Jakarta government has issued bylaws regulating the opening of nightspots during Ramadan. Freestanding bars and nightclubs are supposed to close for the whole month. Enforcement of the laws is patchy, and police and government officials are easily bribed to turn a blind eye.