A 2-mile-high (5km) plume of ash has exploded from a volcano near the capital of Ecuador, coating highways, homes and cars with grey powder before sunrise.

The authorities have restricted members of the public from accessing the park that surrounds the Cotopaxi, which is a popular mountaineering spot.

Cotopaxi became active for the first time since 1877 in April, and is considered one of the world's most dangerous because of its proximity to a heavily populated area, and its glacial cover which makes it prone to fast-moving volcanic rock and mud flows.

However, government scientists have said that the snow-capped volcano, which towers at 5,987m high (19,600ft) and is 30 miles (50km) from Quito, does not seem to be on the verge of a major eruption.

Patricio Ramon of Ecuador's geophysics institute explained that the explosions were an example of small phreatic eruptions.

Such volcanic activity occurs when molten rock meets water and causes steam to violently release.

“The situation merits the population staying informed about what's happening with the volcano,” Ramon told Teleamazonas TV.

People near to the volcano have been tweeting dramatic footage of the activity.