They have also warned that fresh activity at the crater threatened to trigger another deadly wave. Previously, the number of displaced -- including many left homeless -- stood at 22,0000 but that figure has now jumped to just over 40,000, according to the latest tally.
Some 7,202 people suffered injuries, jumping from 1,495, while nearly 1,300 homes were destroyed as the waves crashed into the coastlines of western Java island and south Sumatra, authorities said.
"We're recommending that people who lived near the beach be permanently relocated," national disaster agency spokesman Sutopo Purwo Nugroho told a press briefing in Jakarta.
"But it's a last-ditch option because it's not easy with limited space and people reluctant to move away." A no-go zone around rumbling Anak Krakatoa has been widened to five kilometres -- up from a previous two kilometres -- with residents warned to stay away from the coast.
The crater's status has been raised to high alert, the second-highest warning on Indonesia four-point danger scale. Flights are being redirected away from the area.
A section of the crater -- which emerged at the site of the Krakatoa volcano, whose massive 1883 eruption killed at least 36,000 people -- collapsed after an eruption and slid into the ocean, triggering Saturday night's killer wave.
Before and after satellite images taken by Japan's space agency showed that a two square kilometre chunk of the volcanic island had collapsed into the water.
Indonesia, a vast Southeast Asian archipelago, is one of the most disaster-hit nations on Earth due to its position straddling the so-called Pacific Ring of Fire, where tectonic plates collide.
The tsunami was Indonesia's third major natural disaster in six months, following a series of powerful earthquakes on the island of Lombok in July and August and a quake-tsunami in September that killed around 2,200 people in Palu on Sulawesi island, with thousands more missing and presumed dead.