Russell Crowe films UFO
Russell Crowe films UFO (ParallelUniverse1234/YouTube)

Russell Crowe believes he has captured an unidentified flying object on film over the Royal Botanic Gardens in Sydney.

The Les Miserables actor was trying to photograph fruit bats when he and a friend spotted a flying object moving across the Australian sky.

He then uploaded the photos to YouTube, saying: "Time lapse photos outside RC's office in Woolloomooloo ... These are real ... UFO?"

On Twitter, Crowe said: "A friend and I set camera to capture fruit bats rising from Botanic Gardens. This was a big surprise."

Explaining how he captured the UFOs, the actor said he used a Canon 5D with no flash. When one user suggested the lights may have been a lens flare, Crowe said: "Can't be a lens flare because it moves, camera is fixed."

The YouTube video shows a neon red and yellow-coloured rectangular-shaped object moving from right to left across the sky.

Crowe said he was around 250 metres from the gardens when he snapped the UFO.

One Twitter user, Kevin Cheung, suggested the UFO could be a reflection from the glass window that the camera was positioned in front of, adding that it could be a tail light from a car.

However, the actor debunked this theory, saying: "The camera is on a balcony not behind glass."

Australia has had its fair share of UFO sightings. In January, a father and son filmed what they thought was a UFO in Cardwell in Queensland.

Greg Smith said he saw two large orange lights in the sky: "There was no beam and no noise. It was absolutely silent and they were moving slowly across the sky towards the north-west," he told the Townsville Bulletin.

"We couldn't tell if the lights were from one or two machines. At first we thought they were over buildings between the highway and the beach, but other people said they were just out over the water."

He added that the UFO could not have been a plane as the lights did not flash on and off.