In retaliation for the terrorist attacks in Paris on Friday, the French military conducted a series of bombings against Islamic State sites in Syria throughout Sunday and Monday.

CNN reports French warplanes targeted a command center, a recruitment center, a training facility, a storage base and various other sites in the Syrian city of Raqqa, considered the de facto capital of the extremist organization.

France's air force, l'Armée de l'Air, posted videos on Facebook of fighter jets taking off to raid the city.

According to USA Today, the French Defense Ministry claimed at least 20 bombs were dropped on Raqqa. The jets took off from Jordan and the United Arab Emirates, with the cooperation of U.S. forces.

France has long been a member of the U.S.-led coalition against ISIS, but these attacks have been the strongest offensive waged by the nation. They come in the aftermath of the worst attacks Paris has experienced since World War II.

ISIS claimed responsibility for the series of simultaneous shootings and bombings that rocked the French capital on Friday, leaving at least 129 people dead.

French Interior Minister Bernard Cazeneuve on Monday called the terrorist attacks a declaration of war.

"It is not they who will destroy the Republic," said Cazeneuve. "The Republic will destroy them."

The anti-ISIS activist group, Raqqa is Being Slaughtered Silently, has documented the campaign through social media.

The group claimed there were 24 airstrikes and 30 explosions overnight. The suburbs seemed the primary target, but the museum and stadium, which ISIS reportedly uses as a jail, were also hit.

Few militant deaths were recorded, as ISIS may have retreated in anticipation of the French retaliation. Apparently, no civilian casualties have been reported.

One of the sites hit, the group noted, was the same place where American hostage Kayla Mueller died.

Mueller was a human rights activist taken hostage by ISIS militants in Syria. The terrorist group claims she was killed by a Jordanian airstrike in February 2015.