Australia warned on Friday that terrorists are at an advanced stage of planning terror attacks in Indonesia (search).

The warning came in an updated advisory that Australian travelers should avoid Indonesia unless their travel there is absolutely necessary.

"We continue to receive a stream of credible reporting suggesting that terrorists are in the very advanced stages of planning attacks in Indonesia," the Department of Foreign Affairs and Trade said.

"Attacks could occur at any time, anywhere in Indonesia and could be directed at any locations known to be frequented by foreigners," it said in a statement.

The advice said the truck bombing at the gates of the Australian Embassy in Jakarta (search) which killed 10 people in September last year "underscores that the threat to Australians in Indonesia is real."

The upgraded travel warning follows two anthrax (search) at the Indonesian Embassy in Australia. Suspicious powder sent to the embassy twice in less than a week proved to be harmless.

Prime Minister John Howard (search) warned the scares could provoke retaliation from Indonesians. The travel warning mentioned no link between the white powder hoaxes and the alleged terrorist plans in Indonesia.

Indonesian officials have described the scares as attempts to intimidate their country.

The Australian government suspects they are linked to the 20-year sentence imposed on Australian woman Schapelle Corby last month for smuggling 9 pounds of marijuana into the Indonesian tourist island of Bali.

"Recent credible reporting suggests that international hotels frequented by Westerners in Jakarta are being targeted in current terrorist planning," the travel advice said.

"Public statements by the Indonesian National Police (POLRI) that security has been increased at a number of Jakarta hotels due to the potential for terrorist attack underline that international hotels are a target," it added.

The travel advice follows an Indonesian police warning last month of possible further suicide bombings in Jakarta.

The police identified as potential targets places frequented by foreigners, in particular embassies, international schools, office buildings and shopping malls.

Australians are advised to avoid all travel to Aceh and Maluku province, particularly Ambon. "Australians in Aceh and Maluku should depart," the statement said.

"We continue to receive reports that terrorists may be planning attacks against foreigners involved in the tsunami relief effort in Aceh and other parts of northern Sumatra," it added.