Colombia raised Wednesday the alert status of its most active volcano to its highest level and ordered the evacuation of 8,000 people after it began spewing smoke and ash.

Although the pre-dawn eruption at 4:00 am local time (0900 GMT) was not considered major, officials placed the Galeras volcano in the western department of Narino near the border with Ecuador on red alert.

"The volcano is in a very unstable phase," said Martha Calvache, under director of the state geological service, adding that it was "emitting ash, and lava has been detected in the crater."

Galeras is the country's most active volcano with a half dozen eruptions over the past two years and officials said it was difficult to know what to expect.

"There's no way of knowing if it's going to be the same or worse than earlier ones," Narino governor Antonio Navarro said in the provincial capital Pasto.

Civil authorities issued an evacuation order for some 8,000 people living near the flanks of the volcano, but said that, so far, some 332 people have moved to shelters in the area.

National Emergency director Carlos Ivan Marquez was disappointed: "The community's response has not been great, it's been minimal."

A 1993 eruption of Galeras, which rises in the Andes mountain chain to an altitude of 4,276 meters (14,029 feet), killed nine people, including six scientists who had descended its crater to take gas samples.

Officials from Colombia's Institute of Geology and Mining say the once-dormant volcano reactivated in 2004.

Galeras erupted again in November 2009 leading authorities to evacuate about 1,000 people although no one was hurt. Most recently, the mountain rumbled back to life briefly last January.