A loud sonic boom was heard in Paris on Wednesday as a military jet broke the “sound barrier”, creating panic among the residents, AFP reported. The sound barrier or sonic barrier is the sudden increase in aerodynamic drag – a force that opposes an aircraft’s motion – when it approaches the speed of sound.

“A very loud noise was heard in Paris and in the Paris region,” the police in the French capital tweeted. “It was not an explosion, it was a fighter jet crossing the sound barrier.” They also urged the people to stop calling emergency numbers.

The impact of the sound shook windows. It was heard all across the city.

It was not immediately evident why a fighter plane was flying over the city. A defence ministry spokesperson confirmed to Reuters that the sound was a sonic boom, but did not divulge any more details.

The city’s residents took to Twitter to share videos of the incident. In one video, the boom was heard during a French Open match.

The sound caused panic among the residents as it came less than a week after at least two people were injured in a knife attack near the former office of satirical magazine Charlie Hebdo in the city.