A yellow alert has been issued in Ecuador after four explosions inside the Cotopaxi volcano sent ash flying more than 5 kilometres into the air, CNN reports.

However, no calls for evacuations have been made yet. Yellow alerts warn residents to take precautions and to be prepared in case evacuations become necessary.

Even though the country's scientists say that the volcano is not close to eruption, authorities have closed access to the peak as well as the area around it.

The volcano's last major eruption was in 1877, but some renewed activity was spotted in April.

According to Patricio Ramon of Ecuador's geophysics institute, the blasts inside the volcano could be termed as phreatic eruptions, caused by molten rock or magma colliding with water,

Cotopaxi is one of the most dangerous volcanoes in the world as it is located close to a city and its glacial cover attributes to fast moving volcanic flow, reports RT.com.

The ash coming out of the volcano could reach the cities of Latacunga, Machachi and Quito on Friday, officials at the Geophysics Institute told the state news agency Andes, reports CNN.

In Japan, the meteorological agency issued a level 4 emergency warning, urging the residents to evacuate after Sakurajima Volcano showed increased activity on Saturday.