"In the Sunda Strait 40 people have died, 584 people were injured and two people are missing," Indonesia's National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said in a statement. Another three people were killed in nearby Serang, he added.
Nugroho tweeted on his verified account that 430 houses and nine hotels were heavily damaged, indicating the tsunami hit residential and tourist areas.
Scientists from Indonesia’s Meteorology and Geophysics agency said it could have been caused by undersea landslides from the eruption of Anak Krakatau, a volcanic island formed over years from the nearby Krakatau volcano. They also cited tidal waves caused by the full moon.
The Sunda Strait between the islands of Java and Sumatra connects the Java Sea to the Indian Ocean.
The deaths were reported in the Pandeglang, South Lampung and Serang regions.
The worst affected area was the Pandeglang region of Banten province in Java, which encompasses the Ujung Kulon National Park and popular beaches, the disaster agency said. Of the deaths, 33 were in Pandeglang.
In the city of Bandar Lampung on southern Sumatra, hundreds of residents took refuge at the governor’s office.
The disaster management agency warned that the death toll is likely to rise further, adding that high seas as a result of the full moon may also have contributed to the strength of the waves.
Indonesia has been hit by a series of natural disasters in recent weeks, including a powerful earthquake that hit the island of Sulawesi on September 28. In the towns of Baleroa and Petobo, rivers of soil swept away entire neighborhoods in the aftermath of the magnitude-7.5 earthquake and ensuing tsunami.
The death toll from the quake is nearly 2,000.
In October, torrential rains and flooding triggered mudslides that wiped out part of an elementary school in Indonesia's North Sumatra. Twenty people were killed.