Eight Indonesian airports, including two serving Jakarta, remained closed early on Monday (Sep 7) because of volcanic ash from eruptions of Mount Anak Krakatau, the transport minister said.

Ash from Anak Krakatau, which sits halfway between Java and Sumatra islands, has blanketed Jakarta and several surrounding areas since it erupted late on Friday, leading to the closure of the airports for safety reasons.

"We cannot ascertain when this will end due to the dynamic weather," Transport Minister Dudy Purwagandhi said in a statement on Monday, adding that the eight airports, which included the ones serving Jakarta's nearby provinces of Lampung and West Java, would remain closed until at least 8.59am (9.59am, Singapore time).

Jakarta's Soekarno-Hatta airport subsequently posted on Instagram that flight operations would remain suspended until 6pm local time.

Singapore Airlines is among the airlines affected, with 18 flights cancelled on Monday. Another flight on early Tuesday departing Jakarta was also cancelled.

The transport ministry said 170,000 people have been affected by flight cancellations.

The volcano monitoring agency's website showed the most recent Anak Krakatau eruption occurred Sunday at 8.23pm.

The eruptions have seen ash reach as high as 6,000m on the Java side of the volcano and 15,000m on the Sumatra side and some parts of Banten province in Java, meteorological agency BMKG posted on its website.

On Sunday, the disaster agency called for people to wear masks while travelling outdoors due to the ash. In Jakarta and Lampung, schools will use remote learning to counter health risks for students, state news agency Antara reported.

Indonesia sits on the Pacific "Ring of Fire", where earthquakes and volcanic eruptions are frequent.

Anak Krakatau, which means child of Krakatau, began emerging a century ago from the area previously occupied by Krakatau, then known as Krakatoa. 

The older volcano destroyed itself in mass eruptions in 1883, which killed more than 36,000 people in a series of tsunamis.

Source: Reuters