Indonesia has been put on alert and flight warnings have been issued after Mount Sinabung, on Sumatra island, erupted again.

A red notice has been issued to airlines, which means that the mountain is erupting at a fast-pace and spewing volcanic ash into the atmosphere making it unfit for planes to travel, reported the Guardian. The Mount Sinabung has been sending plumes of smoke and ash as high as 7 kilometers.

The volcano had been dormant for over four centuries before it erupted in 2010, in which two people were killed. Mount Sinabung then erupted in 2014 killing 16 people, and the 2016 explosion killed seven. However, no fatalities or injuries have been reported after the February 19 eruption.

This eruption is the strongest eruption in five years, according to the UN Office for Disaster Risk Reduction and it left streets and surrounding villages smeared in thick ash and debris. 

Ash from Mount Sinabung volcano in Indonesia rises to an approximate height of 5,000 meters as flight warnings have been issued in the countryReuters

A few airports in the region have been closed after the volcano exploded and Sutopo Purwo Nugroho, a spokesman for Indonesia's Disaster Agency, said that the eruption also brought with it multiple earthquakes and a shower of small rocks.

"In five districts it became dark with a visibility of about 5 metres," Reuters quoted him as saying.

Speaking of the airports Nur Isnin Istianto, head of the regional airport authority, told Reuters that the Kutacane airport in Aceh province had been closed, Kualanamu, Meulaboh and Silangit airports were open as they remained unaffected by the smoke and ash.

Authorities have now asked residents to be ready for evacuation and watch out for lava flow. 

Twitter has been abuzz with users talking about the Mount Sinabung eruption and several images and videos of it have also been posted. 

Mount Sinabung is one of the 120 active volcanoes in Indonesia. Last year, the island nation witnessed Mount Agung in Bali rumbling and spewing ash. The highest level of alert was sounded in the region and hundreds of residents were moved to safer locations.

Mount Agung had not witnessed any seismic activity in the last few years, but at the end of September 2017, over 700 incidents were recorded in just one day and the strongest tremor was measured at 4.3 on the Richter scale.