Thousands of residential buildings in southeastern Turkey collapsed in the wake of the 7.8 magnitude quake that hit at 4:17 am, killing many in their sleep.

Two years after the earthquake, dubbed the "disaster of the century" by President Recep Tayyip Erdogan, 670,000 survivors still live in containers.

Many of them are waiting to see if their names will be drawn in a government lottery to receive new homes from the state.

Nearly 201,500 homes have been given to survivors in the vast region affected by the earthquake, and some 220,000 more are expected to be handed over by the end of the year, according to the urban planning ministry.

"Whenever I enter a room, the first place I look is the ceiling: would it hold up in an earthquake, or would I be trapped under the rubble?" said Sema Genc, whose home in Antakya collapsed on top of her, killing her entire family.

"That fear is always with you," the 34-year-old told AFP.

Two years on, 189 people have been sentenced to prison over the disaster, many for negligence, according to the justice ministry. There are 1,342 trials involving 1,850 defendants still under way.

- 'Big one' in Istanbul?

Among the remembrance ceremonies expected on Thursday, Erdogan is due to visit Adiyaman, one of the provinces worst hit by the strong tremors, which killed over 8,000 people there. More than 53,500 people died in total in Turkey and 6,000 in Syria.

Ozgur Ozel, the leader of the main opposition CHP party, condemned on Wednesday in Adiyaman "unfulfilled promises" by Erdogan, who had promised in the spring of 2023 during the electoral campaign to rebuild more than 300,000 homes in one year.

At the same time, repeated earthquakes in recent days in the Aegean Sea, near the Greek island of Santorini, have raised fears of a major tremor that could affect the southwest of Turkey.

On Tuesday, Turkey's urban planning minister Murat Kurum warned about the risk of a "big one" in Istanbul, the country's largest city.

Its southern shores are only about 15 kilometres (nine miles) away from the North Anatolian faultline.

In 1999, a rupture on this fault caused a 7.4-magnitude earthquake, killing 17,000 people, including 1,000 in Istanbul.

"Istanbul does not have the strength to withstand another earthquake" of such magnitude, Kurum said.

He predicted that "millions of our Istanbul brothers and sisters live in 600,000 homes that could collapse".