China's Jade Rabbit Moon rover is in trouble after experiencing a "mechanical control abnormality", state media report.
The Moon exploration vehicle ran into problems due to the moon's "complicated lunar surface environment", Xinhua news agency said, citing science officials.
The rover landed in December as part of China's Chang'e-3 mission - the first "soft" landing on the Moon since 1976.
It was expected to operate for around three months.
Earlier this month, the Beijing Aerospace Control Centre said that Jade Rabbit, also known as Yutu, had successfully explored the surface of the Moon with its mechanical arm.
The malfunction emerged before the rover entered its scheduled dormancy period on Saturday, Xinhua reported, citing the State Administration of Science, Technology and Industry for National Defence (SASTIND).
Scientists were organising repairs, the news agency added, without providing further details.
The rover was due to become dormant for 14 days during the lunar night, when there would be no sunlight to power the rover's solar panel, reports said.
The malfunctioning rover presents the first public mishap China's ambitious space programme has experienced in years, following several successful manned space flights, the BBC's Celia Hatton in Beijing reports.
Xinhua said the news of the rover's troubles had generated extensive discussion on Chinese social media.
"People not only hailed the authority's openness to the accident, but also expressed concern," it said.
On Sina Weibo, China's largest microblog provider, users began tagging their posts with the hash tag "#hang in there Jade Rabbit".
User Jessica_S_AC_USK wrote: "I want to cry. Go Jade Rabbit, even if we fail this time, we still have next time - our Chinese Jade Rabbit's goal is the sea of stars! We will not give up easily."
Referring to a Chinese folktale about a rabbit on the Moon, another microblog user wrote: "Whatever happens, we must thank Jade Rabbit. When our generation tells stories to our children, we can confidently say: 'There really is a Jade Rabbit on the moon!'"