Five people were killed and churches set on fire in Niger on Saturday in fresh protests against the French weekly Charlie Hebdo's Mohammed cover, as France condemned the violence and defended freedom of expression.
With France still reeling from last week's attacks that claimed 17 lives, jittery European countries stepped up security, with soldiers patrolling the streets of Belgium for the first time in 35 years.
But anger mounted in several Muslim countries over the satirical newspaper's caricatures of the Prophet Mohammed, with a second day of rioting erupting in Niger, a predominantly Muslim former French colony.
Around 1,000 youths wielding iron bars, clubs and axes rampaged through the Niger capital, hurling rocks at police who responded with tear gas.
At least eight churches were torched and the French embassy in Niamey urged its citizens to stay at home.
"In Niamey, the tally is five dead, all civilians," Niger's President Mahamadou Issoufou said in a speech broadcast on state television, as he appealed for calm.
The death toll from riots a day earlier in Niger's second city of Zinder had climbed from four to five after a body was found "burned inside a church", he added.
French Foreign Minister Laurent Fabius condemned "the use of violence" in Niger while President Francois Hollande said France was committed to "freedom of expression", calling it "non-negotiable".
Some 15,000 people also rallied in Russia's Muslim North Caucasus region of Ingushetia against Charlie Hebdo, which depicted on its most recent cover a weeping Mohammed holding a "Je suis Charlie" sign.
There were also protests in Pakistan on Friday, and in Gaza the French cultural centre was defaced with graffiti, reading: "You will go to hell, French journalists".
In a speech, Hollande urged his compatriots not to change their habits, because "to do so would be to yield to terrorism."
However, he warned that "nothing will be like it was before" the attacks that rocked France last week.
- 'They have to be punished' -
The deployment of troops in Belgium came after security forces this week smashed a suspected Islamist "terrorist" cell planning to kill police officers.
Greek anti-terror police arrested at least four people suspected of links to the dismantled jihadist cell. Among them was believed to be Abdelhamid Abaaoud, the 27-year-old alleged mastermind of the cell who according to media reports may have been planning the foiled attacks from Greece.
As authorities try to close in on jihadist cells around the world, Yemen detained two Frenchmen for questioning over suspected links to Al-Qaeda
In France, investigators were focusing on 12 people detained early Friday and questioned over "possible logistical support" they may have given to the Paris gunmen -- Islamist brothers Said and Cherif Kouachi and Amedy Coulibaly, sources said.
In London, authorities were mulling "further measures" to protect police "given some of the deliberate targeting of the police we have seen in a number of countries across Europe and the world."
British police officers, for the most part unarmed, will reportedly be equipped with taser guns as part of reinforced security measures.
- Secret burial -
Said Kouachi, one of the jihadist brothers who gunned down 12 people at Charlie Hebdo's offices before being cut down by security forces in a siege, has already been buried in secret, it emerged on Saturday.
He was buried Friday in the northeastern city of Reims, where he lived for around two years, under heavy police protection and with a handful of family members present, according to a well-informed source.
His grave was unmarked and the name of the cemetery was not divulged. His brother Cherif was expected to be buried soon in the Paris suburb of Gennevilliers.
The mayor of Reims, Arnaud Robinet, said he was forced by law to accept the burial but was initially opposed to the gunman being buried in his city.
He feared "a tomb that could become a shrine for people to gather around or a pilgrimage site for fanatics."
Said Kouachi's wife decided not to attend the burial in order to keep it secret, said her lawyer Antoine Flasaquier
"She is now relieved that her husband has been buried with discretion and dignity," the lawyer said.
Charlie Hebdo, which has flown off the shelves in record numbers since the attacks, announced on Saturday it would extend its print run to seven million copies.
Before the assault on its Paris headquarters, Charlie Hebdo had a circulation of around 30,000, with only a handful being sold abroad.