Australia and Canada warned Wednesday about fresh threats of terrorism and kidnapping in the southern Philippines, and Canberra barred its diplomats from travelling to three cities in the area.

Both urged their citizens not to travel to large parts of the Mindanao region, with the Australian government specifically barring its diplomats from the cities of Davao, Cotabato and Zamboanga.

An Australian embassy spokeswoman told AFP the travel ban went into effect from Monday and until further notice.

"We have a duty of care to ensure the safety of staff overseas," she said. The embassy declined to discuss any specific threats.

The Canadian embassy advised its citizens to avoid all travel to most parts of Mindanao "due to the serious threat of terrorist attacks and kidnapping".

It said the advisory was issued Tuesday and was still valid Wednesday. Embassy spokesmen could not be reached for comment.

The Australian Department of Foreign Affairs and Trade website said the new advisory for the Philippines concerned terrorism and serious crime.

The United States embassy in Manila had already warned its citizens on May 29 of a "credible kidnap threat against foreigners in Zamboanga", it added.

In late 2002 Australia and Canada closed their Manila embassies for more than a month due to an unspecified terrorist threat. Both missions later moved to a new building.

Mindanao is the hotbed of a decades-old Muslim insurgency. President Benigno Aquino is aiming to sign a peace treaty with the Moro Islamic Liberation Front, the largest guerrilla force there, before 2016.

The island is also the stronghold of the Abu Sayyaf, Islamic militants with links to Al Qaeda who have staged deadly bombings and kidnappings of foreigners for ransom.

In March Abu Sayyaf militants released Australian Warren Rodwell after holding him for 15 months. An undisclosed ransom was paid.

Other Abu Sayyaf factions are believed to be holding other hostages, including two European bird watchers.

US troops have been based in the southern Philippines for more than a decade to help train local troops in hunting down members of the group.