Indonesian police have placed radical Muslim cleric Abu Bakar Ba'asyir under arrest in connection with alleged terrorist activities across south-east Asia.

Governments in the region as well as the United States have been demanding that he be arrested for months, accusing him of having links with the terrorist network al-Qaeda.

Mr Ba'asyir is recovering in hospital in the city of Solo after he collapsed on Friday ahead of being questioned in connection with bomb attacks on churches in 2000.

An Indonesian Foreign ministry spokesman told the BBC that the police were acting on information that alleged Mr Ba'asyir was behind previous bombings in Indonesia and even plots to kill the president.

Although under arrest, the cleric will remain in hospital until he has recovered.

At least 10 people died in the church bombings in 2000

The move came as Australia warned it had received intelligence about plans for bomb attacks on Westerners in the Indonesian capital, Jakarta.

In another development, the Indonesian Defence Minister Matori Abdul Jalil told a news conference in Bali that he still believed the al-Qaeda network was behind the night-club bombing.

However, he did not reveal his evidence.

He also said he did not anticipate any backlash against the arrest of Mr Ba'asyir.

There was a small demonstration outside the hospital where the cleric is being held, but it remained peaceful.

Senior police officials went to the hospital in Solo on Saturday morning to check that Mr Ba'asyir was in fact ill.

According to a senior Muslim leader, they then handed an arrest warrant to Mr Ba'asyir's lawyers.

Shadowy group

The cleric is suspected by some governments of leading the shadowy Jemaah Islamiah group - a charge he denies.

Indonesia has linked Jemaah Islamiah to Osama Bin Laden's al-Qaeda network.

Authorities suspected him of involvement in a spate of church bombings across Indonesia in December 2000. The US, Malaysia and Singapore have been demanding his arrest for months.

Correspondents say there is no evidence linking him to the Bali bombing.

New alert

Australian Foreign Minister Alexander Downer said on Saturday he had "specific threats... of bomb attacks in... certain [Jakarta] suburbs against Westerners" and urged Australians to leave.

We have received reports that crowded areas, including upmarket entertainment areas, should be avoided

Australian Foreign Ministry

"On the basis of intelligence we've received, it's very important we draw people's attention to the risk," he said.

The Australian foreign ministry has issued a travel advisory asking citizens to avoid the Jakarta suburbs of Kota, Jalan Hayam Wuruk, Taman Anggrek, Pasar Baru and Pasar Senen.

"We have received reports that crowded areas, including upmarket entertainment areas, should be avoided," the ministry says on its website.

It adds that the possible arrest of "extremist leaders" in the wake of the anti-terrorism decrees passed by Indonesia on Friday could provoke a "strong reaction from their supporters".

Families grieve

The announcement came as Australia received the first positively identified remains of one of its citizens killed in the Bali night-club bombing.

The coffin containing the body of Angela Golotta, 19, arrived in Adelaide on Saturday draped in the Australian flag.

Angela would have been celebrating her 20th birthday this week.

At least 183 people were killed in the Bali bombing, more than 100 of them believed to be Australian.

Australian Prime Minister John Howard said on a solemn visit to Bali on Friday that he sympathised with the families of the bereaved waiting for the return of their loved ones' bodies.

But he said the identification process needed to be thorough and carried out properly to avoid any errors.

Australia will observe a day of national mourning on Sunday.

Investigators sifting through the wreckage of the Bali night-club have now been joined by American experts who were involved in the investigation at the World Trade Center site in New York.