"We must be conscious that since 1980 wherever championships have been held, even in nations with high security measures, there have always been some problems with public order," Nuno Magalhaes told reporters following a meeting with police chiefs in the southern Algarve resort province.

"The times of greatest risk are normally not during or after matches but before, even days before, when fans start congregating," he added.

At the last Euro football finals, which were jointly hosted by Belgium and the Netherlands in 2000, some 850 mostly English fans were arrested following hooliganism in the centre of Brussels and in nearby Charleroi, Belgium's third biggest city.

In an effort to avoid a repeat of such scenes during Euro 2004, which will take place between June 12 and July 4, Portugal has cancelled all police leave for what will be the biggest sports event ever held in the country.

The Portuguese government is spending 16.5 million euros (21 million dollars) to equip police with seven water cannon vehicles - the country's first - as well as batons, riot gear, pepper spray and other security equipment.

Portugal has also drawn up plans to set up round-the-clock courts that will have the power to quickly expel potential troublemakers and is mulling an alcohol ban around stadiums on game days.

Euro 2004 organizers meanwhile switched the venues of two first-phase group games which were deemed "high-risk" by European ruling body UEFA to stadiums in bigger cities where it would be easier to offer a strong police presence.

The Group D match on June 14 between Germany and the Netherlands was moved from the central fishing town of Aveiro to Oporto, Portugal's second-largest city, while the June 20 encounter in Group B between England and Croatia was moved to Lisbon from the university town of Coimbra.

Portugal is hoping a peaceful Euro 2004 will give its key tourism industry a big boost. Up to three million people are expected to travel to the country this year because of the football finals.