Mount Sinabung, one of the most active volcanoes in Indonesia, erupted again on Saturday, shooting a column of ash 4,000 meters to the sky as the number of evacuees rose, official said.

Powerful burst of hot ash and gravel erupted from the rumbling volcano, located in Karo district of North Sumatra, at least 30 times since Saturday morning and hot ash has slid off by up to 5 kilometers from the crater to southeast, pushing the authorities to extend evacuation zone to 20 km from 5 km previously, Sutopo Purwo Nugroho, spokesman of national disaster agency said.

"The column of hot ash now is the biggest ever compared with those frequently spewed (since the volcano erupt in Sept.) The hot ash has slid off to the southeast, covering two villages," he told Xinhua by phone.

The authorities evacuated all the villagers on Friday, adding the total number of displaced person to 20,331 on Saturday from 19, 286 on the previous day, said Sutopo.

Besides, the authorities also extended emergency relief period ended on Jan. 5 to Jan. 18, he said. "The people are recommended to persistently be cautious and abide the authorities' guidance," said Sutopo.

The 2,457-meter Mount Sinabung in Karo district of North Sumatra has rumbled to life since September after being quiet for 400 years. It has erupted on and off since then, but went into overdrive frequently in November and December.

On. Dec. 31, Mount Sinabung erupted, spewing ash 7000 km to the sky, one of the strongest since September.

The Mount Sinabung is among the 129 active volcanoes in the vast archipelago country, which is prone to seismic upheaval as it lays on the Pacific "Ring of Fire" encircling the Pacific Ocean.