The Australian government on Friday warned Australians in the United States to be alert to their own security.

Australia's Department of Foreign Affairs and Trade (DFAT) reissued its travel advisory to the United States after New York City authorities announced Thursday that they have increased security measures, including additional police presence, on New York City's subway system after receiving a credible threat of a terrorist attack.

New York Mayor Michael Bloomberg has been briefed on the threat by the FBI which suggested New York's underground train network could be attacked within days.

"Australians in the United States are advised to be alert to their own security. As you would in Australia, use common sense and be alert to suspicious activities," the DFAT said in the updated travel advisory for Australians issued Friday.

"Travelers can expect additional scrutiny of personal belongings, including inspection of bags and luggage, when traveling on the subway system," it said.

Australians in the United States are also advised to avoid areas affected by Hurricane Katrina and Hurricane Rita due to significant communication, transport, and infrastructure damage.

Source: Xinhua