Ecuador's President Rafael Correa declared a state of emergency Saturday as the dangerous Cotopaxi volcano rumbled to life and prompted evacuation orders in several villages threatened by landslides.

"As a precautionary measure, a total of 400 people have been evacuated," the president said in his radio and television address just before signing the decrees.

The volcano, which towers to 5,897 meters (19,350 feet) high, is considered one of the most threatening in the region -- both because of its size and because it is so close to well-populated towns.

"The situation developing at Cotopaxi is a serious threat that has led the government to take urgent special measures to confront this eruptive process," said Public Safety chief Cesar Navas.

- Second day rumbling -

The volcano started to stir Friday, registering several small eruptions and angrily shooting plumes of dust and ash eight kilometers (five miles) into the sky.

By declaring a state of emergency -- also called a state of exception in Ecuador -- the president can direct resources and deploy military personnel to aid communities affected by the volcano's activity.

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, just 45 kilometers south of the capital Quito, were told to clear out, said Pablo Morillo, head of the Risk Management Office.

Officials did not specify how many people could be affected by the evacuation order which affects three provinces with towns near the volcano.

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, along with cars carrying mattresses, motorcycles and other household items.

- Yellow alert -

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 said.

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 Friday as they fled villages, with a large, angry cloud of gray dust and ash forming over Cotopaxi.

The Environment Ministry has declared the volcano off limits to tourists, and 15 climbers who were preparing to scale the mountain were sent home 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.