Jakarta, Sep 26 (IANS): Some 75,000 people were evacuated due to increasing frequency of tremors around Mount Agung, a large volcano on the Indonesian island of Bali, authorities announced on Tuesday.

"Mount Agung is entering a critical phase. Although alert level 4 (the maximum) has been declared since September 22, there is no guarantee that the volcano will erupt," an official from the National Disaster Mitigation Agency said.

Mount Agung's volcanic activity continued to increase and its magma was moving closer towards the surface, he added.

On Monday, the observation post at Mount Agung recorded 547 volcanic earthquakes, a figure which quadrupled from 119 quakes registered on September 22, which, together with other parameters, indicated that magma levels were likely to be ascending, reports Efe news.

The agency estimated that about 80,000 residents were living within a 12-km radius around the crater in the Karangasem district which has been designated as an exclusion zone.

Indonesian Red Cross workers placed warning signs at the entrance to the perimeter.

Local authorities reassured tourists that it was not dangerous to visit the island, and Bali's Ngurah Rai International Airport continued to operate normally. However, embassies have warned of possible flight cancellations in the event of an eruption.

The agency had said in a statement on September 21 that the current tremors were similar to those that occurred before Mount Agung erupted in 1963, which killed over 1,100 people.