Belgium is deploying hundreds of troops to guard possible terrorism targets as the head of Europol has warned further attacks could not be ruled out.
Much of Europe is on heightened security alert after last week's killings in Paris and raids in Belgium
Up to 300 Belgian military will be stationed at locations such as Jewish sites and, US and Israeli embassies in Brussels and NATO and EU institutions.
“It‘s very important to say that this wasn‘t a simple decision, but it was necessary, at a time when police are overly engaged, for the army to enter in a supporting role,” Belgan defence minister Steven Vandeput told reporters.
Troops will reinforce police at least until Thursday, when authorities will review the national threat level, set at 3 on a scale of 4 this week.
Meanwhile Europol director Rob Wainwright said the threat of terror attacks is an “urgent and very serious challenge” and large-scale and long-term problem.
“Stopping everything is very difficult, containing the threat fully is very difficult, but I’m sure we will prevail, as we have prevailed against other forms of terrorism in the past,” Mr Wainwright told Sky News.
Asked whether he was saying there was no guarantee attacks such as those in Paris could be stopped, he said: “No, there can’t be, otherwise what happened in Paris wouldn’t have happened. I think there is a realisation across the police and security community in Europe.
Elsewhere British prime minister David Cameron is in the United States for two days of talks with president Barack Obama where they have said they would tackle the threat posed by extremists.
Meanwhile French president Francois Hollande said on Saturday that anti-Charlie Hebdo protesters in other countries do not understand France's attachment to freedom of speech.
He was speaking a day after the satirical weekly‘s publication of a cartoon of the Prophet Muhammad sparked violent clashes, including deaths, in some Muslim countries.
Demand has surged for Charlie Hebdo's first issue since two militant gunmen burst into its weekly editorial conference and shot dead 12 people at the start of three days of violence that shocked France.
The magazine’s distributors said that its print run had been lifted to seven million copies, dwarfing its usual circulation of only 60,000.
A cartoon image of Muhammad on its front page outraged many in the Muslim world, triggering demonstrations that turned violent in Algeria, Niger and Pakistan on Friday.
“We’ve supported these countries in the fight against terrorism,“ Hollande said during a visit to the southern city of Tulle, traditionally his political fiefdom.
“I still want to express my solidarity (towards them), but at the same time France has principles and values, in particular freedom of expression,“ he added.
Teargas in Niger
Police in Niger fired tear gas on Saturday at hundreds of rock-throwing protesters in a second day of clashes over Charlie Hebdo’s publication of the image. Two churches were also set on fire.
France‘s embassy in Niamey advised its citizens against going out in the streets and urged caution because of the risk of demonstrations.
Five people were killed on Friday in the Zinder, the second city of the former French colony, while churches were burned and Christian homes looted. The death toll was revised up after a burned body was discovered in a Catholic Church.
Protests also turned violent on Friday in the southern Pakistan city of Karachi where police used tear gas and a water cannon against demonstrators outside the French consulate.
A photographer for French news agency Agence France-Presse was also wounded by a gunshot during the protest.
Several Algerian police officers were injured in clashes with demonstrators in Algiers after rioting broke out at the end of a protest.
“There are tensions abroad where people don‘t understand our attachment to the freedom of speech,” Mr Hollande said. “We‘ve seen the protests, and I would say that in France all beliefs are respected.“
Produced by survivors of the attack on the newspaper, the latest edition of Charlie Hebdo sold out in minutes when it hit newsstands on Wednesday. It shows a cartoon of a tearful Mohammad holding a “Je suis Charlie“ sign under the words “All is forgiven.“
A lawyer for one of the gunmen in the Charlie Hebdo attack said the man had been buried in the eastern city of Reims in an unmarked grave so as not to attract admirers.
The Belgian government raised the threat level after a raid in the town of Verviers on Thursday in which police shot dead two gunmen. Authorities said the Islamist cell had been preparing an attack on police.
The first military company to be deployed on Belgium‘s streets was the Chasseurs Ardennais, an infantry unit from the Ardennes region.
Among the places the soldiers are protecting in Brussels is the Jewish Museum, which last May was the site of an Islamist attack, when a lone gunman burst into the then unguarded site and killed four people.
There will also be soldiers in Antwerp, the country‘s second largest city, which has a large Jewish community, the minister said.
“In Antwerp the largest threat is there,” Mr andeput said, referring to the Jewish community. “It is also where people are most worried.”
Troops with machineguns were on guard outside Jewish schools in Antwerp, while in Brussels soldiers were standing outside EU institutions.
The raids in Verviers on Thursday drew attention to the large number of Belgians drawn to fighting in Syria and elsewhere in the Middle East, then returning home radicalised.