Chile's imposing southern Llaima volcano roared into action Thursday, spewing rocks, lava and clouds of ash and putting six nearby communities under a red alert, the National Emergency office said.

"Activity has strengthened, but it is all taking place in the Calbuco river sector, where we have all precautionary measures in place," Cautin Province Governor Andres Jouannet told reporters.

He said the 3,125-meter (10,253-foot) volcano 700 kilometers (1,100 miles) south of Santiago erupted in the predawn hours, after six months of quiet following its initial eruption on January 1.

"You can see three (lava) flows heading for the Calbuco river, which is constantly being monitored for abnormal levels," the office said in a statement.

It said six communities in the vicinity of the volcano a week ago were placed under a red alert, pending immediate evacuation should the situation worsen.

Llaima was Chile's second erupting volcano this year, after the 1,000-meter (3,280-foot) Chaiten volcano, 100 kilometers (65 miles) further south awoke after centuries of lying dormant in May.