A loud bang heard across north London and the surrounding region was a Sonic boom from military planes investigating an aircraft that had temporarily lost communication, the U.K. Ministry of Defence said on Twitter.
Typhoon jets were scrambled after an aircraft lost communications, it said. The aircraft was intercepted and communications re-established. The Typhoons have now returned to their base.
"There is no cause for public concern,” the police said earlier, adding that there were no reports of an explosion. The noise came days after a terror attack on London Bridge left two civilians dead.
Hundreds of U.K. residents reported the boom across London around 4:20 a.m. Many said their houses were shaking and police sirens could be heard in the north of the city. Twitter users reported hearing the noise from parts of London to as far as Cambridge, 50 miles to the north of the capital.
