Singapore's Ministry of Defence (MINDEF) has addressed a loud boom that was heard and felt across Perth, Western Australia on Aug. 21.

In a reply to media queries on Aug. 22, MINDEF said that four Republic of Singapore Air Force (RSAF) F-15 aircraft have been training out of Royal Australian Air Force (RAAF) Base Pearce, a military airbase north of Perth, from Aug. 13.

Initial findings revealed that the boom was likely to be caused by the training fighter jets, said MINDEF.

Loud boom heard and felt across Perth

According to Australia news outlet ABC News, local authorities had looked into reports of a "loud booming sound" heard and felt across a large area of Perth's southern suburbs on Aug. 21.

The incident occurred just before noon and affected areas such as Mandurah, Fremantle and Byford.

Locals sharing about the incident on social media reported cases of rattled windows and "shaking" houses.

Planes can cause sonic booms when they break the sound barrier by travelling faster than the speed of sound — about 1,223kph at sea level.

Such loud booms occur when shock waves are produced as a plane moves through the air, and the shock waves collide with each other.

Likely caused by RSAF aircraft training, MINDEF apologises

According to MINDEF, the fighter jets had flown about 70km from the coast at above 24,000 feet in the designated training area.

The aircraft were in restricted navy airspace off Garden Island, reported ABC News.

When the boom occurred, the airspace stretching from the coast near Busselton to north of Perth had been active for military operations.

MINDEF said: "The loud noise was unexpected as the F-15 was far out at sea."

The ministry apologised for any alarm caused by the training activity and added that the RSAF appreciates the continued support by the RAAF and the local community for the training.

The training is expected to end on Sep. 6.

Top photo via Defence Australia/Facebook