THE HAGUE -- The Netherlands has raised its terrorism alert level to "substantial" because of the planned release of an anti-Islam film by a far right politician, the justice ministry said Thursday.

"While there is no concrete indications of impending attacks in the Netherlands, the increased international terrorism threat has prompted to raise the threat level for the Netherlands from 'limited' to 'substantial'," the ministry said.

"Compounding the threat is the fact that the Netherlands has been cast in a negative light in the Islamic world due to the tone of the debate on Islam in this country, especially since the announcement of a controversial film on the Koran," the statement added.

Far right deputy Geert Wilders has said that his short movie -- which he says attacks the Koran as a "fascist book" -- will air in March.

The international media attention for Wilders movie "has led to the posting of death threats against the Freedom Party leader on one of the leading international jihadist web forums", according to the national anti-terrorism coordinator NCTb.

Other factors, such as the Dutch government's decision to extend the mandate of Dutch troops fighting in Afghanistan, were also taken into account in raising the threat assessment, it added.

In light of thwarted terrorist attacks in Germany and Denmark in December 2007 and in Spain in January of this year motivated by the presence of Western troops in Afghanistan, "this is a real source of risk for the Netherlands".

The Wilders film has caused uproar in Muslim countries, some of whom have called for an economic boycott of the Netherlands if the film is shown.

The Dutch government has twice tried and failed to convince Wilders not to broadcast his film, fearing a repeat of the worldwide protests which met the publication of satirical Danish cartoons of the prophet Mohammed.

The Taliban in Afghanistan have already threatened retaliation against Dutch soldiers in the country if the film is broadcast.