Lindsay Murdoch, Jakarta – Police snipers guard buildings housing United States government agencies and businesses. Sales of T-shirts bearing the face Osama bin Laden are brisk. Mobs of Islamic radicals search hotels for Americans, threatening to expel them. And security is high at the Australian Embassy after newspapers played up Saturday's attack on a mosque in Brisbane.

Observers in the world's largest Islamic nation, Indonesia, are increasingly worried about the possibility of a violent backlash to the US military build-up in the Middle East and South Asia.

Police have failed to act against public threats to attack the US Embassy despite an appeal for action by the ambassador, Mr Robert Gelbard, and Indonesia's Defence Minister, Matori Abdul Djalil.

The Front of Islamic Defenders, which boasts 10,000 members, yesterday renewed threats to launch a jihad, or holy war, against US interests in Indonesia. It also warned it would bring down President Megawati Sukarnoputri if she backs US-led strikes in Afghanistan.

The group's leader, Habib Muhammad Rizieq, has been quoted in the Indonesian press as saying that the Front would "curb the space for American visitors" if Muslims are killed. "If we want to participate in a jihad we don't need to go to Afghanistan. We can launch a jihad against America here," he said, adding that Islamic groups would "launch acts to ruin [Ms Megawati's] position" if she returned from her current trip to the US and implemented US policies.

Ms Megawati has promised US President George Bush Indonesia's support for his war against terrorism. The country's Foreign Minister, Hassan Wirayuda, said yesterday that Indonesia would ratify several United Nations conventions to lay a firm legal basis for fighting terrorism. "We deem it necessary to strengthen our legal instruments at home," he said.

Western intelligence officials have information that the bin Laden organisation has sent agents to Indonesia to attack US interests.