Apr 18, Kathmandu- More than 11,000 displaced people have been evacuated after a volcano erupted in the North Sulawesi province of Indonesia, according to Al Jazeera.

Mount Ruang exploded once on Tuesday and four times on Wednesday.

Indonesia's volcanology agency has raised the alert level of the mountain to four, the highest on the scale being 700 meters high.

The agency has extended the size of the exclusion zone around the crater from four to six kilometers. Initially, more than 800 residents of Ruang were moved to Tagulandang Island.

Officials say more people have to be evacuated and brought to Manado because of the growing exclusion zone.

"At least 11,615 residents of the risk area should be moved to safer places," Abdul Muhari, head of the disaster data, communication and information center of the disaster agency, was quoted as saying by Al Jazeera.

Officials are concerned that part of the volcano may have fallen into the sea and caused a tsunami, as in the 1871 eruption.

Sam Ratulangi International Airport in Manado will remain closed until at least Thursday evening. According to aviation officials, the spread of volcanic ash, which may pose a threat to flight safety.

The airport offers flights to other countries including South Korea, China and Singapore. Flights to and from the nearby Kota Kinabalu International Airport in Malaysia have also been severely disrupted.

After two earthquakes this week, Mount Ruang has seen an increase in activity, according to the country's Volcanology Service.