Four people were killed when their boat capsized in choppy seas in Indonesia.

The 16 passengers were riding the speedboat called Cinta Putri when they were battered by large swells off Nunukan Regency in North Kalimantan province, at around 11 am today.

They were thrown overboard when a powerful wave struck the watercraft. Witnesses on the shore called rescue teams after seeing the passengers struggling in the choppy seas.

Indonesian Navy Colonel Handoyo said in a statement: 'We have ordered a search and rescue. One victim was found dead during the search.'

In a later report, authorities said four people were found drowned. They were identified as Acay, his wife who was not named by officials, Solerang, and Gisman.

Eight passengers were rescued and taken to the Nunukan Regional Hospital. Volunteers were still searching for four missing people.

A local named Yudha Aji said: 'I was riding a speedboat from Simanggaris to Nunukan when I saw many people drowning in the water because their speedboat overturned.

'We managed to rescue five victims, whom we took to the Sei Bolong Pier. I asked them what happened but they weren't sure either. There are a lot of corals and seaweed on the path. It's possible the boat hit them, or was struck by the waves, but I'm not sure.'

The maritime accident happened just a day after three schoolchildren were killed by a rip tide in East Java. The schoolchildren had been swimming in choppy waters at Drini Beach when they were dragged out to sea by the currents.

Rescue officers said three pupils were killed. They were identified as Alfian Aditya Pratama, 13, Malfen Yusuf, 13, and Bayhaki F, 13. Another pupil, Rifky Yudha Prataman, 13, was missing.

The local meteorological agency warned of 'extreme weather' occurring in North Kalimantan province until February 1.

Weather forecaster Ida Bagus Gede Yamuna Ceswaraningrat said today: 'In addition to sea surface temperatures, there are also wind bends and wind meetings, so there will be an accumulation of wet air masses which will cause an increase in rain clouds or cumulonimbus clouds.'