Nasa scientists have contributed to a spate of UFO sighting videos sweeping the internet.

The US space agency were filming from a shuttle outside the earth's orbit in April this year when the cameras picked up four objects that have never been identified.

The footage came after two similarly eerie sightings a few days apart on different sides of the world.

In January this year an amateur cameraman was one of a crowd who gathered to look at a mysterious light in the sky above Mexico.

He captured images of a trail dragging behind a very slow-moving object in the sky, before another light appeared on the horizon.

In the same week, a group of teenagers in India stopped by the side of the road and captured a group of glowing objects moving in patterns in the sky.