This massive swarm of crows screeching as they circled around building tops amidst a thick fog startled local residents who suddenly found themselves in what almost appeared to be a scene from a horror film.

One resident, surnamed Xu, filmed the apocalyptic sight in the city of Tianjin, China, on October 30.

Xu said his attention was first drawn by the sound of a chaotic cacophony outside the window. When he pulled back the curtain, he was astonished to see countless black birds hovering above the residential area.

Phone footage shows a large flock of crows circling around the tops of residential buildings amid gloomy weather and a grey sky that made the area look like a horror scene.

Another clip shows them gathering on the rooftops, filling the air with the sound of their loud croaking.

A third piece of footage filmed from the ground shows the countless crows covering the sky above.

Experts later explained the situation as a natural phenomenon that can often be observed among migratory bird species that search for warmer weather.

Wen Cheng, an avian expert from Peking University's School of Life Sciences, said: 'The birds that gather in large flocks overnight in the city include swallows, white wagtails, sparrows, and crows.

'The main reason they concentrate in the city overnight is that it's warmer or there are fewer predators in the city. 'Such situations often occur from the beginning of autumn until the arrival of winter.'