Iran's President Hassan Rouhani on Wednesday warned that insulting the Prophet Mohammed may encourage "violence and bloodshed" following Paris' defence of the publication of cartoons depicting the Prophet.

Iran has summoned a senior French envoy, the charge d'affaires, to protest Paris' defence of the publication of cartoons depicting the Prophet Mohammad, the foreign ministry in Tehran said.

Turkish President Recep Tayyip Erdogan on Monday joined calls for a boycott of French goods, ramping up a standoff between France and Muslim countries over Islam and freedom of speech.

France will pay tribute Wednesday to a history teacher beheaded for showing cartoons of the Prophet Mohamed in a free speech lesson in a gruesome attack that has shocked the country and prompted a government crackdown on radical Islam.

French authorities said Tuesday they would close a Paris mosque as part of a clampdown on radical Islam that has yielded over a dozen arrests following the beheading of a teacher who had shown his pupils a cartoon of the Prophet Mohammed.

For the second time in three weeks, terror struck France, this time with the gruesome beheading of a history teacher in a street in a Paris suburb. The suspected attacker was shot and killed by police.

French President Emmanuel Macron denounced what he called an "Islamist terrorist attack" and urged the nation to stand united against extremism. The teacher had discussed caricatures of Islam's Prophet Muhammad with his class, authorities said.

Millions of French people enjoyed a last night of freedom on Friday before a Covid-19 curfew in Paris and other large cities came into force at midnight, for a least a month, prompted by an alarming surge in new cases.

France on Wednesday became the latest European country to toughen anti-coronavirus measures, imposing a curfew in Paris and eight other cities from Saturday, while Germany and Ireland also ramped up restrictions. 

"We have to act. We need to put a brake on the spread of the virus," President Emmanuel Macron told public television, announcing a shutdown between 9:00 pm and 6:00 am that will remain in force for as long as six weeks.

Over the course of a single overnight shift this week, three new COVID-19 patients were rushed into Dr. Karim Debbat's small intensive care ward in the southern French city of Arles. His service now has more virus patients than during the pandemic's first wave, and is scrambling to create new ICU beds elsewhere in the hospital to accommodate the sick.

Similar scenes are playing out across France. COVID-19 patients now occupy 40% of ICU beds in the Paris region, and nearly a quarter in ICUs nationwide, as several weeks of growing infections among young people spread to vulnerable populations.

More than half the people living in extreme poverty in the Paris region, in particular migrants, have been infected with the new coronavirus, the French aid group Doctors Without Borders (MSF) said Tuesday.