French security troops are to guard the fronts of all Catholic and Protestant churches for the coming Easter weekend, a memo to officials said on Thursday.
France wants to bolster its security after raising its threat alert to the highest level after the Moscow concert hall attack that claimed at least 143 lives.
The massacre was the deadliest attack in Russia in two decades, with ISIS claiming responsibility.
In a memo sent to prefects on Thursday and seen by AFP, Interior Minister Gerald Darmanin said the "very high" level of terrorist threat and persisting international tension, including the Gaza war and the Moscow attack, mean that "extreme vigilance must be maintained" during the Easter celebrations.
Mr Darmanin asked prefects to post police in front of "all" Catholic and Protestant churches, in particular during services on Friday and this weekend.
He said "particular attention" should be paid to vehicles parked near places of assembly or worship.
Two planned attacks have been foiled in France since the start of the year.
One involved a plot to stage "violent action against a Catholic religious building" by a man "clearly committed to [extremist] ideology", according to the national anti-terrorist prosecutor's office.
Gunmen open fire in Moscow concert hall - in pictures
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A memorial next to the Crocus City Hall, on the western edge of Moscow, Russia. AP Photo -
Russian law enforcement officers at the site of a deadly gun attack on the Crocus City Hall. AFP -
A makeshift memorial in front of Crocus City Hall, a day after the gun attack. AFP -
The damaged Crocus City Hall after the attack, which was claimed by ISIS. AP Photo -
People attend a vigil in honour of the Moscow concert gun attack victims in the centre of Simferopol, Crimea. AFP -
Laying flowers in memory of the Moscow victims, in Simferopol. AFP -
The vigil in Simferopol, Crimea. AFP -
A digital board with a date and a slogan that reads 'We mourn' opposite Crocus City Hall. Reuters -
Emergency services personnel and law enforcement officers outside the hall after gunmen opened fire at concertgoers. AFP -
A fire spread through the building after the attack. AFP -
A firefighting helicopter douses flames at Crocus City Hall. AP -
Fire rises above the Crocus City Hall following the shooting. EPA -
Officers stand guard near the burning Crocus City Hall. Reuters -
Russia tightened security at airports, transport hubs and across the capital - a vast urban area of more than 21 million people. AP -
All large-scale public events were cancelled across the country. AFP -
A medic stands near ambulances parked outside the burning concert venue. AP -
Plumes of black smoke rise above Crocus City Hall after the attack. Reuters -
Members of Russian special operations forces gather at the building after the shooting. Reuters -
Smoke rises above the venue following the shooting. Some witnesses reported explosions. Reuters -
Investigators and intelligence services officials at the scene after the attack. AP -
An assault rifle lies on the ground as investigators work at the scene. AP -
Russian firefighters at the venue. EPA
The man, 62, was arrested and remanded in custody in early March, prosecutors said.
Catholics and Protestants celebrate the resurrection of Jesus on Easter Sunday, while Orthodox Christians hold their Easter on May 5.
