European nations arrested dozens of Islamist suspects Friday as Belgium said it had smashed a "terrorist" cell planning to kill police officers and France pursued fresh leads on last week's Paris attacks.
The raids renewed fears about the thousands of young Europeans believed to have gone to the Middle East to fight with the Islamic State and Al-Qaeda-linked groups before coming home to launch attacks.
Two suspected jihadists were shot dead in a fierce gunbattle with police during an anti-terror raid in the eastern Belgian town of Verviers, near the German border, on Thursday night, prosecutors said.
Police arrested 13 people during a series of raids across Belgium, five of whom were later charged with "participating in the activities of a terrorist group", federal prosecutors' spokesman Eric Van der Sijpt told AFP.
He earlier told a news conference that the group, some of whom had recently returned from Syria, was "on the verge of carrying out terrorist attacks to kill police officers on public roads and in police stations."
Police found four Kalashnikov rifles, explosives, ammunition and communications equipment during the raids, along with police uniforms.
Jihadist Twitter accounts later identified the two dead men as Radwan Haqawi and Tareq Jadoun and published what it said was a photo of them in Syria. Belgian authorities did not confirm their identities.
Two other Belgians were arrested in France after allegedly fleeing the raids and were headed towards Italy, police sources said. Belgium has asked for their extradition.
Belgian prosecutors said there were no immediate links with last week's Islamist attacks in Paris on the Charlie Hebdo satirical magazine, a Jewish supermarket and a policewoman, in which 17 people died.
French police separately arrested 12 people overnight and questioned them about "possible logistic support" they may have given to the Paris gunmen -- Islamist brothers Said and Cherif Kouachi and Amedy Coulibaly, sources said.
In Germany an alleged leader of a Turkish and Russian group planning to carry out an attack in Syria and the man in charge of financing were arrested in raids on suspected Islamist sites in and around Berlin by more than 200 police officers, officials said.
- Security boost -
The tide of arrests came as politicians pledged to boost security in the face of what they said was a growing Islamist threat.
Belgian Prime Minister Charles Michel said he was ready to call up the army to ensure security in the wake of the raids. He raised the country's terror alert to three on a scale of four.
Jewish schools in Brussels and the port city of Antwerp closed Friday. The raid comes less than a year after four people were shot dead in an attack on the Jewish Museum in Brussels. A Frenchman who fought in Syria has been charged with the murders.
With France still reeling from the attacks which targeted its cherished traditions of free speech, US Secretary of State John Kerry laid wreaths on Friday at both the Charlie Hebdo offices and the Jewish supermarket during a visit to Paris.
French President Francois Hollande meanwhile urged the world to offer a "firm" and "collective" response to the attacks, which drew 1.5 million people into the streets in Paris in their wake along with dozens of world leaders, although the US was not among them.
In Washington, President Barack Obama said during a visit by Prime Minister David Cameron that the United States and Britain would help France "seek the justice that is needed" after the attacks.
Charlie Hebdo, which inflamed Muslims in many countries by printing cartoons of the Prophet Mohammed, also laid to rest its editor-in-chief Stephane Charbonnier, alias cartoonist Charb, on Friday.
International anger over Charlie Hebdo's printing of a new image of Mohammed in its sold-out comeback issue this week continued to rage, with protesters clashing with police outside the French consulate in the Pakistani port city of Karachi.
AFP photographer Asif Hassan was shot in the back while covering the protest but appeared to be out of danger following surgery.