JAKARTA: Indonesia's Anak Krakatau volcano located in the waters of the Sunda Strait erupted on Tuesday, spewing an ash cloud of about 1 km high, an official said.

The volcano's Observation Post Officer Anggi Nuryo Saputro said the eruption occurred at 6.29 a.m. for 130 seconds, with the wind heading north, reports Xinhua news agency.

"The ash column was observed to be gray to black in colour with thick intensity towards the north," he said in a statement.

Since it first emerged in June 1927, Anak Krakatau's volcanic activity has been on the rise, making its body larger and taller, up to 157 m above the sea level. Its activity has increased significantly since April last year, which raised its dangerous status to the third highest level.

In 2018, Anak Krakatau erupted and triggered a tsunami that killed over 400 people and left thousands homeless.