Speaking on Indonesian television, President Joko Widodo made a brief statement.

"I want to express my deep sorrow for the victims in Serang, Pandeglang and Banten Province," he said, adding: "May those who survived be patient."

Initially the disaster agency spokesman, Sutopo Purwo Nugroho, said the wave was not a tsunami, but a tidal surge, and told the public not to panic.

He has now apologised for the mistake, saying there had been confusion because no earthquake had been recorded.

Witnesses have described the moment the tsunami hit areas around the Sunda Strait and the chaos that followed.

Asep Perangkat told AFP news agency that he was with his family on Carita beach on Java when the wave surged through the town, carving a path of destruction.

"Cars were dragged about 10m (32ft) and so were containers," he said.

"Buildings on the edge of the beach were destroyed, trees and electricity poles fell to the ground. All the residents that are safe ran to the forest."

Alif, a resident in Pandeglang district on Java, told MetroTV that many residents were still searching for missing relatives.

In Lampung province, on Sumatra, 23-year-old Lutfi Al Rasyid told AFP: "I could not start my motorbike so I left it and I ran... I just prayed and ran as far as I could."

In the city of Bandar Lampung, hundreds of residents took refuge at the governor’s office, AP news agency reports.

Indonesian officials are warning people to stay away from the coastline due to fears of further tsunamis.

"We're waiting for the updates of [Krakatau's] status if there's any development on its volcanic activity. If its activity is getting worse, we need to be alert," says Rahmat Triyono, head of the national earthquake and tsunami center BMKG.

Indonesia's President Joko Widodo says he's ordered government officials to take emergency measures to search for victims and care for the injured following the deadly tsunami.

In a tweet, he expressed his "deep condolences" to the families of victims.

The death toll from a tsunami on Indonesia's Sunda Strait has risen to 168, a government official says. About 745 others have been injured.

Australian Prime Minister Scott Morrison says "our thoughts go out to all those who have lost loved ones, the injured and all of their families".

"As always we stand ready to assist as needed," he adds.

ABC News Indonesia correspondent David Lipson says the latest information he has received indicates "we are probably talking of a death toll of hundreds at this point".

"We have heard from local agencies both of the southern tip of Sumatra and the western coast of Java," he told BBC World News television.

"On the western coast of Java, one official said that more than 90 people have been killed. In southern Sumatra; more than 110 killed."

The correspondent stresses that those numbers are not official.

Emergency officials in Indonesia are investigating whether the tsunami was caused by undersea landslides after the eruption of Krakatau, a volcanic island in the Sunda Strait.

Volcanologist Jess Phoenix told the BBC that when volcanoes erupt, hot magma pushes underground and can displace and break through colder rock. This can trigger a landslide.

But because part of Krakatau is underwater, she said "instead of just causing a landslide, you get an undersea landslide which pushes water as it moves." This can then cause a tsunami.

Image source, Oystein Andersen

Earth and planetary sciences professor Michael Manga, at the University of California, Berkeley said: “Volcanoes can move the crust up and down - creating the waves that become tsunamis.

“When the flanks [side] of volcanoes collapse, or pyroclastic flows enter the ocean, they can also create waves that become tsunamis.

“Flank collapse may have generated the biggest tsunamis on earth (excluding the very rare ones from asteroid impacts into the ocean).”

But the International Tsunami Warning Center, externalsays events like this are "relatively infrequent".

Norwegian volcano photographer Oystein Andersen (see our earlier entry) has posted a picture of the erupting Krakatoa volcano just a few hours before the tsunami struck.

Andersen was able to move his family to safety before the largest wave struckAnyer beach, where they are staying.

The BBC's Rebecca Henschke in Indonesia says reports from one of the worst-hit areas, Lampung in Sumatra, suggest the death toll could be in the hundreds there.

This has not been officially confirmed by local government officials.

The tsunami hit late at night, there were no warnings, and people had no idea it was coming, our correspondent says.

The Sunda Strait - between the islands of Java and Sumatra - connects the Java Sea to the Indian Ocean.

Deaths have been reported in the Pandeglang, South Lampung and Serang regions.

In Pandenglang, the resort of Tanjung Lesung appears to have been particularly badly hit.

Dramatic footage has emerged on social media showing the moment when the tsunami hit a venue, where a popular Indonesian rock group, Seventeen, was performing.

We have chosen not to show that footage.

In an Instagram video, external, (warning: many may find this distressing to watch) lead singer Riefian Fajarsyah said that the band's bassist and road manager had died, and that three other band members as well as his own wife were missing.

He added that "the rest of us are safe, despite injuries and bone fractures".

Oystein Lund Andersen, a Norwegian volcano photographer, was on the Anyer Beach in West Java when the tsunami struck.

He later told the BBC what happened on Saturday evening.

"I was on the beach. I was alone, my family were sleeping in a room.

"I was trying to photograph the erupting Krakatau volcano.

"Earlier in the evening, there was quite heavy eruption activity.

"But just prior to the waves hitting the beach, there was no activity at all. It was just dark out there.

Image source, EPA

"And suddenly I saw this wave coming, and I had to run.

There were two waves. The first wave wasn't that strong - I could run from it.

"I ran straight to the hotel, where my wife and my son were sleeping.

"And I woke them up... and I heard a bigger wave coming. I looked out of the window when the second wave hit. It was much bigger.

"The wave passed the hotel. Cars were pushed off the road.

"We and other people at the hotel went straight to the forest (on higher ground) next to the hotel."

Image source, Reuters

Indonesia's disaster management agency says the tsunami struck at about 21:30 local time (14:30 GMT) on Saturday.

Agency spokesman Sutop Purwo Nugroho warned that the death toll was likely to rise further, as rescue teams were searching the worst-hit areas.

Some residents have now returned to their homes in the area, trying to salvage whatever they can.

At least 62 people are now known to have died after a tsunami hit the shores around Indonesia's Sunda Strait, government officials say.

Nearly 600 people were injured and another 20 are missing. Many houses were flattened in the area.

Saturday's devastating waves were possibly triggered by undersea landslides after the Krakatau volcano erupted.

Stay with us - we'll be bringing you all the latest reports from our correspondents at the scene, local and international reaction, eyewitness accounts as well as footage and photos from the area.