Ash from Chile's spewing Calbuco volcano threatened on Saturday to make travel miserable as it triggered the cancellation of domestic and international flights in several cities.

A sleeping giant for more than 50 years, the volcano sprang to life in spectacular bursts of ash and lava on Wednesday and Thursday, forcing 6,500 people living nearby to evacuate and blanketing southern Chile in suffocating volcanic debris.

The mountain coughed out more fire and ash on Saturday, with an ash cloud drifting eastward over Patagonia and Argentina, reaching Buenos Aires 2,000 km away. Some airlines there canceled flights to and from the US and Europe.

In the Chilean capital, Santiago, domestic flights operated normally, but some international flights were scrubbed.

A handful of flights were scrapped at Montevideo's Carrasco International Airport, and authorities urged people to use face masks to avoid inhaling ash particles.

"The volcano remains unstable, and eruptions - principally ash - will continue for now," Chile's National Geology and Mining Service said in its latest report.

Experts cautioned that a third eruption may yet follow.

A state of emergency has been in place since Wednesday. Authorities emptied a 20-km radius around Calbuco, which is located in Los Lagos, a region popular with tourists for its scenic mountain landscapes dotted with volcanoes, and its lakes with black sand beaches.

More people were ordered out of towns near Calbuco that were deemed at risk of flooding from snow and ice melting high in the mountains due to the volcano's heat. Authorities said they planned to evacuate about 4,000 sheep and cattle.

"I'm afraid and still thinking about leaving, but over the long term, I would still return to my land," said Carolina Bayern, who took refuge in a school with other evacuees.

Raul Rangel, who also was staying at the school, said he was no longer afraid of the volcano after it took out his home.

"I respect it," he added. "My house collapsed, and everything is destroyed, and I feel such great sadness."

It is the second volcano to erupt in Chile since March 3. The country has about 90 active volcanoes.