Soldiers have fanned out to guard possible targets in Belgium and Greek police detained at least two people in a widening anti-terror dragnet across Europe.
In France, one of the terrorists behind last week's attacks in Paris was given a secret burial as authorities sought to head off glorification of terrorism and civil unrest.
It followed a groundswell of popular antagonism across Europe against radical Islam and protests against caricatures of the Prophet Mohammed across the Muslim world that have underscored vast cultural differences.
For the first time in 30 years, authorities used paratroopers to reinforce police in Belgium's cities, guarding buildings within the Jewish quarter of the port city of Antwerp and some Belgian embassies. The move came a day after anti-terror raids netted dozens of suspects across western Europe and increased anxiety across big swathes of the region.
Belgium has increased its terror warning to three, the second-highest, following the anti-terror raids of Thursday which left two suspects dead. Police believe the cell they largely dismantled was on the verge of a major attack.
Authorities said that even though they had broken up the cell they were still looking for some suspects abroad and briefly hoped Greece could have clinched the breakthrough by detaining one remaining key suspect.
A Greek police source said earlier that the men, detained separately in Athens, 1,500 miles from Brussels, included an individual who at first sight matched the description of a key terror suspect in Belgium.
But after careful vetting of ID information in Brussels, federal magistrate Eric Van der Sypt said later there was no positive match with any individual they sought and said "they had nothing to do with the Belgian case".
With some suspects still at large, it was an uneasy calm in Belgium and paratroopers on the street did not necessarily help.
"You know, when people see the soldiers on streets they will get scared. That could make more problems than solutions," said Antwerp student Greg Verhoeven.
France tried to stave off unrest there when Said Kouachi, one of the gunmen who attacked the offices of the satirical magazine Charlie Hebdo, was quietly buried.
After an initial refusal to provide a burial place for Kouachi, the mayor of Reims, Arnaud Robinet, said he was forced to backtrack. He said the government had insisted he allow the elder brother to be buried in Reims because according to French law, residents of a town have the right to be buried there.
"He was buried last night, in the most discrete, anonymous way possible," Mr Robinet said.
Kouachi and his brother Cherif were killed by French anti-terror police on January 9 after they killed 12 people at the offices of Charlie Hebdo. Cherif Kouachi is to be buried in Gennevilliers, a suburb of Paris where he lived.
There has been no word on plans for the burial of the third gunman, Amedy Coulibaly, who killed five people at a kosher supermarket in Paris before he was gunned down by police.
French authorities also banned an anti-Islamist demonstration in Paris, arguing it might incite civil unrest.
"We are one country, one people, one France - without distinction by religion, belief or sensibility," President Francois Hollande said in south-central France. "An ardent France against those who want to instil among us who knows what war of religion."