This is the eerie moment thousands of crows filled the sky over a motorway in China.

The flock was spotted hovering ominously in the clear blue sky in Anqing, Anhui, on November 6.

Footage shows the black birds flying in different directions - leaving drivers below with an eerie feeling.

Mr Yao said: 'It was creepy. It feels like a bad omen will come.'

On October 26, a murder of crows circled above a hospital in Inner Mongolia.

Officials from the Hongshan District Forestry and Grassland Department attributed the behaviour to the 'urban heat island effect,' which causes cities to remain warmer at night, attracting the crows.

Bird experts caution that crow droppings are highly corrosive and can damage vehicles and clothing if not cleaned promptly.

Crows may gather for various reasons, including mating season, communal roosting at night for protection from predators, ritualised behaviours such as gathering around a deceased fellow to display specific actions, or mobbing predators to drive them away from their territory.