Ecuador's President Rafael Correa said on Saturday he will declare a state of emergency as the Cotopaxi volcano rumbled to life and prompted evacuation orders in several villages threatened by landslides.
Cotopaxi volcano started to stir on Friday, registering several small eruptions and angrily shooting plumes of dust and ash eight kilometres (five miles) into the sky.
By declaring a state of emergency -- also called a state of exception in Ecuador -- the President can access resources and deploy military personnel to aid communities affected by the volcano's activity.
"We will declare a state of emergency based on the activity of the Cotopaxi volcano. Why have I made that decision? To secure resources... to address a potential emergency and mobilise the necessary resources," Correa said in his weekly address.
Earlier, officials ordered what they called precautionary evacuations in villages near the volcano, warning residents of potential landslides of volcanic debris, or lahars.
Residents in towns and river settlements in Cotopaxi province, some 45 kilometres south of the Capital Quito, were told to clear out, said Pablo Morillo, head of the Secretariat for Risk Management.
Officials did not specify how many people could be affected by the evacuation order.
In the city of Latacunga, home to about 170,000 people, sirens sounded as residents frantically fled, packing food, water and pets into cars that quickly clogged the roads.
"I was driving near the Cutuchi river and police came out with sirens, alerting us, and moving from house to house to draw people out. The sirens distressed us," one woman told AFP, without providing her name.
Soldiers could be seen in the streets of Latacunga on Saturday, along with cars carrying mattresses, motorcycles and other household items.
Authorities maintained a yellow alert in the region, a mid-range warning, and said it would remain as long as Cotopaxi continued to stir.
"We will maintain the same alert, but since there are still no lahar flows, the evacuation order is still only preventive," Morillo told AFP.
The volcano, which towers to 5,897 meters high (19,000 feet), is considered to be one of the most threatening in the region -- both because of its size and because it is so close to well-populated towns.
The volcano spewed a current of hot glass and rock -- called pyroclastic flow -- which authorities warned could trigger avalanches or lahars.
"Due to the pyroclastic flows that can generate lahars, preventative evacuations (are ordered) on the southern part" of the volcano, the Risk Management office said on Twitter.
The Geophysical Institute also cautioned residents: "At present there have been no lahars, but they could occur."
Quito mayor Mauricio Rodas said one million surgical masks would be distributed across the city of 2.3 million people, to prevent inhalation of falling dust.
Some residents could be seen wearing masks on Friday as they fled villages, with a large, angry cloud of gray dust and ash forming over Cotopaxi.
The environment ministry declared the volcano off limits to tourists, and 15 climbers who were preparing to scale the mountain were sent home on Friday.
Cotopaxi is one of eight active volcanoes in Ecuador, a country that is part of the so-called Pacific Ring of Fire that makes it prone to seismic and volcanic events.
Its snow-covered tip has been described as "majestic" and is a popular climbing destination.