By Alexandra Valencia
QUITO (Reuters) - Ecuador's massive Cotopaxi volcano stirred in the early hours of Friday, with two small explosions reported and ash raining down on the southern part of nearby highland capital Quito.
Authorities stressed that the explosions and a five-kilometer (3 mile) high plume of ash do not signify that the Andean country's highest active volcano, which has been showing signs of activity since April, is about to erupt.
Still, authorities declared a so-called yellow alert, which signifies "precaution" rather than "evacuation," though evacuation routes were published on the government's Risk Management website. (http://goo.gl/YDbeLD)
"These are the first explosions we have registered since April when (the volcano) started to demonstrate seismic anomalies," said Patricia Mothes, head of volcanology at the Geophysical Institute.
"These are very small explosions, almost imperceptible," she added.
The Environment Ministry closed the Cotopaxi National Park as a precaution and the Institute issued a warning about one of the world's highest active volcanoes, popular with tourists.
"We recommend climbers take precautions around the crater, given the possibility of explosions which release rocks or energetic emissions of vapor and volcanic gases that could be harmful," it said in a statement.
The volcano is located around 50 km (31 miles) south of Quito. Its snow-topped symmetrical cone, which rises to nearly 6,000 meters (19,685 ft), is visible from the capital on a clear day.
Images on social media showed cars and roads near the volcano covered in a light layer of ash.
The last eruption took place in 1940, according to the Smithsonian Institution's Global Volcanism Program.
Friday's minor explosions took place at 4.02 a.m. (0902 GMT) and 4.07 a.m. local time, according to the Geophysical Institute.
(Reporting by Alexandra Valencia in Quito; Writing by Girish Gupta; Editing by Alexandra Ulmer, Marguerita Choy and Dan Grebler)