Cracks have appeared on a U-shaped glass-bottomed skywalk built around a mountain cliff in China, sending tourists fleeing off the structure, Chinese media reported.

Tourists walk on the glass skywalk on Yuntai Mountain YouTube

Internet users posted pictures online showing cracks on the reinforced glass flooring, which is suspended more than 1,000 metres above sea level, around a cliff on Yuntai Mountain in Henan province, the Legal Evening News reported.

The photos sparked an outcry, with internet users alleging that inferior construction material had been used to build the skywalk, which opened to public only about two weeks ago.

Officials said the cracks were caused by tourists who had dropped a thermos flask on the glass.