Australia is investigating claims that Muslim extremists with possible ties to the group accused of carrying out the Bali bombing were granted visas to Australia because they faced religious persecution in Indonesia.

Immigration Minister Philip Ruddock announced the probe after it was reported that Australia's Refugee Review Tribunal (RRT) heard numerous appeals for protection in the 1990s from Indonesians who feared persecution by former dictator Suharto.

A former member of the tribunal told ABC radio that members of Islamic fundamentalist groups in Indonesia had obtained residence in Australia because of claims they faced religious persecution.

Mr Ruddock said investigators were checking whether any visas were granted to people with links to Jemaah Islamiah (JI), the militant Muslim group which some governments accuse of being behind the Bali bombing.

Australia has now outlawed the group as terrorist.

Applications 'unsuccessful'

"I have certainly asked the [immigration] department to check whether there were claims of linkages with JI were accepted as a basis for a refugee claim and a grant of protection," Mr Ruddock said.

Australia has banned JI since the Bali bombs

But he added that he understood that people with links to JI had been unsuccessful in gaining a visa.

Australian Federal Police said they were also looking into reports that several people in the western Australian city of Perth had admitted to JI membership while applying for a visa.

Former tribunal member Bruce Haigh said he believed several Islamic militants were successful in being granted asylum.

"That process I think is continuing, not only amongst people who have come in recently, but people who have been here for a while," he told ABC.

Security alert

The claims came as Australia's security forces were put on heightened alert following Tuesday's announcement by the government that it had received "credible information" about a threat to the country's security.

Australia's international school and embassy in the Indonesian capital of Jakarta also remained closed for a fourth day on Wednesday, following a reported terrorist threat against Western interests.

The US and Jakarta International Schools and the US embassy are also shut.

Indonesia is continuing its hunt for six men it has named as having had a suspected role in the Bali bombing on 12 October.

The country's authorities have also extended the detention of Muslim cleric Abu Bakar Ba'asyir - believed to be the spiritual leader of JI, and suspected of involvement in a string of church bombings across Indonesia in Christmas 2000.

Mr Ba'aysir, who denies any link with JI, and any wrongdoing, can now be held until 31 December.