French anti-terror forces swarmed a forest just outside of Paris on Thursday, hot on the trail of two commando-style gunmen who killed 12 in a bloodbath at the Charlie Hebdo newspaper.

Even as darkness fell on Foret de Retz, authorities vowed to press on, look in every cave and over turn every rock in the pursuit of brothers​ Cherif and Said Kouachi​.

Cops are combing through the forest​ ​as well as the nearby northern French towns of Villers-Cotterets, Longpont and Corcy.

French Interior Minister Bernard Cazeneuve urged citizens not to panic even if two crazed killers are on the loose.

“We need to be calm and show that we are not afraid and that we will remain united in this trial,” he said.

The Kouachi brothers are believed to be the crazed gunmen responsible for Wednesday’s attack on a satirical newspaper, killing 12 people in Paris.

Heavily armed police scoured the 51-square-mile Foret de Retz, which is actually larger in land area than the French capital where the carnage unfolded.

The Interior Ministry said 88,000 police and military personnel were involved in the nationwide manhunt.

“We must prepare ourselves for a hunt that could take several days,” ministry spokesman Pierre-Henry Brandet told iTele.

The grieving nation remained on high alert in hopes the terrorists are captured soon.

“There are lots of policemen. I can see a huge police car. They are asking people ‘Have you seen anybody?’ They have big guns with them,” Longpont hotel worker Benoit Verdun told Sky News.

“The forest is bigger than Paris – it is very big and very wide.”

It’s believed that​ the suspects​​ knocked off a service station in Villers-Cotterêts, stealing fuel and food, according to multiple French media reports.

The gas station manager said the robbery happened at 10:30 a.m. local time and that the two men were armed with Russian-made automatic rifles and rocket-propelled grenade launchers.

Police are searching door to door in the area, maintaining roadblocks and keeping a close eye on the town from helicopters.

“It’s an incessant waltz of police cars and trucks,” said Villers-Cotterêts mayor Bruno Fortier, describing the intense manhunt in his city, about 50 miles northeast of Paris.

The killers are believed to be driving a Renault Clio.

Police are also keeping a close eye on the N2, a highway leading northeast out of Paris to Villers-Cotterêts that could possibly bring the killers all the way to the Belgian border.

Security has been dramatically increased at every border crossing out of France, in case the killers try to drive out of the country, authorities said.