It's the post that inevitably sparks sarcasm and ridicule on social media, but on Sunday night, it was instead curiosity that dominated the conversation in Canberra community Facebook groups.

Hundreds of people reported hearing what sounded like an explosion, described as "a huge echoing boom", somewhere around Holt about 9.03pm.

Many said it shook their houses, while others described seeing an orange flash at the same time and shared images from their CCTV cameras.

While there is no shortage of reports, there are so far no answers on what caused the mysterious bang.

"Police were unable to determine the noise source," an ACT Policing spokesperson said on Monday afternoon, confirming that officers responded to several calls from concerned residents.

"But ACT Policing urges anyone who does know anything about the incident to contact Crime Stoppers on 1800 333 000."

The source of Sunday night's noise may remain a mystery, but more loud bangs are likely to be heard in Canberra over the coming weeks.

The Australian Defence Force plans to carry out counter-terrorism training from mid-to-late August.

The defence force said it was unable to provide further information, including specific timings, in order to protect operational tactics, techniques and procedures.

"The public should not be alarmed if they see or hear military vehicles and military personnel carrying weapons and using blank gunfire and pyrotechnics," the defence force said in a statement.

"People who see the training should not be concerned that any of the locations are under any form of actual threat."