A crop circle in a rice field at Krasakan in Sleman, Yogyakarta.

Discovery of mysterious crop circle – a large, geometric pattern in a rice field in Sleman, Yogyakarta surprised everyone in the city on Sunday.

It was first discovered by a local farmer, Tukiman immediately triggered widespread curiosity including the Indonesian Air Force said to have dispatched a helicopter to photograph the crop circle, which measured 70 meters in diameter, The Jakarta Post reports.

One villager, Cahyo Utomo, of Kraskan speculated the odd circle couldn’t have been man-made.

“The circles were there since yesterday morning. I think they were left by an alien space ship, like one I saw in TV,” he told Jakarta Post.

“It is impossible that this was were made by the wind or any animal,” he insisted.

However, Moedji Raharto offered a more logical explanation of the rare phenomenon which The Jakarta Post said might be the first ever reported in Indonesia.

“If this really is the work of a UFO or extraterrestrial beings, it is almost 100 percent certain they would have left some sort of trace behind.

“The chemical composition of the soil itself could reveal the origin of the phenomenon. For example, when a meteorite enters the atmosphere and forms a crater, it leaves traces of elements that are not common to the area,” Moedji said.

He added that similar results could be expected in a soil analysis of the Yogyakarta circle.

Sleman Police chief Adj.Sr.Com. Iwan Ramaini said he was not sure if the circles were created by a UFO or if it was a natural phenomenon.

A police investigation is underway.