Grace Nirang, Jakarta – Indonesian police said on Sunday they had arrested 65 anti-American demonstrators in Jakarta and would charge them with weapons offences, triggering angry scenes involving hundreds of Muslims outside the police headquarters.

The arrests mark the first clear action against members of radical Muslim groups who have staged small but rowdy demonstrations in Jakarta and other cities over US-led air attacks on Islamic Afghanistan.

Some of those arrested belong to the Islamic Defenders Front (FPI), which has vowed to hunt down Americans and Britons and drive them out of the world's most populous Muslim nation.

"We will process them according to the law even though we are facing the risk of protests. There is no plan to release them," Jakarta police spokesman Anton Bahrul Alam told reporters.

Alam said police found dozens of knives, hammers, arrows and other sharp weapons when they searched about 500 anti-American protesters after they arrived in Jakarta by train from the central Java city of Solo overnight. He said the maximum jail term for the offences was 12 years.

Clad in white robes, the rest of the group who arrived from Solo protested outside the Jakarta police headquarters, occasionally rocking the blocked gates leading into the compound. There were no clashes, and the focus on the police compound appeared to divert attention away from the heavily fortified US embassy for a second straight day.

Solo is home to some of Indonesia's more hardline Muslim groups, who late last month searched hotels in the city for Americans to warn them to leave the country in the event of a US attack on Afghanistan.

Anti-American feeling has spilled onto the streets in Indonesia, but has been confined to the radical groups whose actions and threats against foreigners have been criticised by the majority moderate Muslim populace.