With the ultimatum issued by Osama bin Laden's al-Qaeda terrorist network to be expired on Thursday, the Netherlands was on high alert on terrorist attacks on Wednesday.

The Dutch secret service AIVD confirmed on Wednesday that the looming al-Qaeda deadline contributed to the intensified alert issued for the Netherlands since last Friday.

Three months ago, Osama bin Laden warned a number of European countries of attacks if their troops were not withdrawn from Iraq, Afghanistan and other Islamic countries. The ultimatum he gave expires on Thursday.

This is the first official explanation of the high levels of security at many sites in the Netherlands including Amsterdam's Schipol airport, Radio Netherlands reported.

Armored police wagons and extra police officers moved into surveillance positions at key Dutch infrastructure points last Friday after the AIVD warned the government it has indications that Islamic extremists might be preparing a terrorist attack.

Dutch Prime Minister Jan Peter Balkenende has since urged the public to remain vigilant. He has also said the public should not be alarmed with the visible additional security measures.

The Netherlands has troops in Afghanistan and Iraq and has recently confirmed commitments to a continued Dutch military presence in both countries. The Dutch are involved in security and reconstruction operations.

The Netherlands also gave political, but not military support to the US-led war against Iraq, potentially opening up the risk ofterrorist retaliations.

But the al-Qaeda ultimatum is not the only reason for the terror alert. Information has been received from various sources, prompting the Dutch Cabinet to declare the heightened terror alert.

Source:Xinhua