At least 222 people have been killed and 843 were injured on the Indonesian islands of Java and Sumatra when a tsunami struck areas around the Sunda Strait late on Saturday following an undersea landslide caused by a volcano.

Key points: The tsunami was the result of an underwater landslide caused by volcanic activity

The tsunami was the result of an underwater landslide caused by volcanic activity Pandeglang regency, Serang, and South Lampung were inundated with water

Pandeglang regency, Serang, and South Lampung were inundated with water Indonesian authorities have said they are not aware of any foreigners affected

Disaster agency spokesman Sutopo Purwo Nugroho said the disaster was caused by "a combination of an undersea landslide resulting from volcanic activity on Anak Krakatoa and a tidal wave".

Not all the affected areas have been reached and Mr Nugroho said the death toll may still rise.

At least 28 people were missing.

Sorry, this video has expired Police rescue child from rubble after tsunami hits western Java in Indonesia

Up to 430 homes were reported as being heavily damaged, along with nine hotels and 10 vehicles.

According to a statement from the Meteorology, Climatology and Geophysics Agency, the tsunami hit "several areas of the Sunda Strait, including beaches in Pandeglang regency, Serang, and South Lampung".

The tsunami struck despite no "significant" seismic tremors to indicate one was coming. ( AP )

The tsunami struck about 9:30pm local time, sending a wall of water 19 metres inland.

The worst affected area was the Pandeglang region of Banten province in Java, which encompasses the Ujung Kulon National Park and popular beaches, the geophysics agency added.

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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.

Indonesian President Joko Widodo expressed his sympathy and ordered government agencies to respond quickly to the disaster.

"My deep condolences to the victims in Banten and Lumpung provinces," he said.

"Hopefully, those who are left have patience."

Up to 430 homes have been reported as heavily damaged, along with nine hotels. ( AP: Dian Triyuli Handoko )

Prime Minister Scott Morrison said Australia would provide assistance if required.

"We understand that at present there are no foreigners, let alone Australians, who have been impacted by this," Mr Morrison added.

US President Donald Trump also offered support for Indonesia via Twitter, saying: "We are praying for recovery and healing. America is with you!"

Footage posted on social media showed a pop band named Seventeen performing under a tent on a beach as dozens of people sat listening at tables covered in white cloths.

The stage suddenly heaved forward, throwing the band and all their equipment into the audience.

A man inspects his destroyed house in the aftermath of the tsunami in Carita, a district of the Pandeglang Regency. ( AP: Dian Triyuli Handoko )

The group released a statement saying their bass player, guitarist and road manager were found dead, while two other band members and the wife of one of the performers remained missing.

"The tide rose to the surface and dragged all the people on site," it said.

"Unfortunately, when the current receded our members are unable to save themselves while some did not find a place to hold on."

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Tourist Oystein Lund Andersen was taking photos of the volcano when he said he saw a large wave.

"I had to run, as the wave passed the beach and landed 15 to 20 metres inland," he wrote on Facebook.

"Next wave entered the hotel area where I was staying and downed cars on the road behind it.

"Managed to evacuate with my family to higher ground through forest paths and villages, where we are taken care of [by] the locals."

He said he and his family were unharmed.

Sorry, this video has expired Video of the aftermath shows knee-deep water flooding streets.

Endan Permana, head of the National Disaster Mitigation Agency in Pandeglang, told Metro TV that police were providing immediate assistance to victims in Tanjung Lesung in Banten province, a popular tourist getaway not far from Jakarta, as emergency workers had not arrived in the area yet.

"Many are missing," Mr Permana said.

There was initial confusion over the tsunami, with Mr Nugroho initially tweeting that the flooding was the result of extreme tides caused by the full moon.

Mr Nugroho corrected his tweets hours later, confirming it was a tsunami after receiving updated data.

He said the eruption of Krakatoa was "not large" and added there were no "significant" seismic tremors to indicate a tsunami was coming.

Evacuated residents shelter inside a mosque in Pandeglang regency. ( Reuters/Antara Foto: Muhammad Bagus Khoirunas )

Gegar Prasetya, co-founder of the Tsunami Research Centre Indonesia, said the tsunami waves were likely caused by a flank collapse, which occurs when a big section of a volcano's slope gives way.

He said it was possible for an eruption to trigger a landslide above ground or beneath the ocean, both capable of producing a tsunami.

"Actually, the tsunami was not really big, only one metre," Mr Prasetya said.

"The problem is people always tend to build everything close to the shoreline."

The Anak Krakatoa volcano in the Sunda Strait that links the Indian Ocean and Java Sea erupted about 24 minutes before the tsunami, creating a column of volcanic ash estimated to be up to 500 metres high, according to the geophysics agency.

The 305-metre-high volcano — about 200 kilometres southwest of capital Jakarta — has been erupting since June.

The death toll is expected to rise as authorities continue to comb through affected areas. ( AP: STR )

In July, authorities widened its no-go areas to two kilometres from the crater.

In September, at least 832 people were killed by an earth quake and tsunami that hit the city of Palu on the island of Sulawesi, which is just east of Borneo.

Krakatoa's most recent eruption was in October last year.

Anak Krakatau volcano spews smoke and lava into the Sunda Strait in November, 2007. ( Reuters: Supri )

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