A mystery black ring baffled residents after it was seen moving across the sky in Mexico.

The strange figure was seen floating above streets in Ciudad Obregon in Sonora on September 21.

One of the residents said some of his confused neighbours panicked when they saw the black smoke ring over their homes.

He said: "Some were joking about aliens and UFOs, but others were seriously scared about it.

''One person thought that it was birds or thousands of insects invading the area, but it was moving too slow.''

The rare smoke ring phenomenon is believed to have been caused by an explosion from a circular structure. The dense smoke mixes with gases and retains its ring structure while it is suspended in the atmosphere.

Locals believe the explosion may have happened at a nearby factory. There was also a car seen burning in the street,

The smoke dissipated after almost half an hour of drifting high above the homes.