"We haven't got anything on that," UN mission spokesman Bill Bergman told

"We get various rumours at times, unsubstantiated rumours, but nothing that has developed into an issue that an alert has been issued."

The Danish foreign ministry said in a statement that it had "received information that a terrorist attack was forthcoming against humanitarian organisations in the Aceh region."

It gave no further details but called on humanitarian aid workers and journalists to "exercise the greatest caution and try to stay safe" and "immediately inform other people in the region".

The UN's humanitarian coordination office (OCHA) in Geneva said relief staff in the region had been advised to "be aware of the situation" but there was no official alert from the world body.

"It's a kind of common sense advice to be extremely vigilant," OCHA spokeswoman Elisabeth Byrs said.

The inter-governmental International Organisation for Migration, which is playing a leading role in the distribution of foreign aid throughout Aceh, also had not received any reports of a terrorist threat.

"The situation is obviously a complex one here but no, we haven't heard anything like that," said IOM spokesman Chris Lom.

Aceh, which bore the brunt of the December 26 tsunamis, is the scene of a three-decade conflict between government forces and separatist rebels, but both sides say their operations will not affect the relief effort.

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