The death toll is the worst in the country’s history. Its previous worst mining disaster was in 1992 when a gas explosion killed 263 workers near the Black Sea port of Zonguldak.

Violent protests have erupted in Istanbul as citizens accuse the government of covering up the number of dead to avoid international criticism over the safety standards at the mine.

Police were seen firing tear gas and water cannons to disperse a crowd of several thousand demonstrators.

Prime Minister Recep Tayyip Erdogan declared three days of national mourning, ordering flags to be lowered to half-staff.

"We as a nation of 77 million are experiencing a very great pain," he told a news conference after visiting the site.

He then appeared on the defensive when asked whether sufficient precautions had been in place at the mine.

"Explosions like this in these mines happen all the time,” Erdogan said.

“It's not like these don't happen elsewhere in the world," he said, listing many of the global mining accidents since 1862.

Carbon monoxide poisoning is believed to have killed most of those confirmed dead and the government warned that rescuers faced a race against time.

The death toll has been rising rapidly since 787 workers became trapped inside the mine on Tuesday.

The Istanbul-based company has 5500 employees and is one of the region's major coal producers, with 2.5 million short tons mined annually, according to its website.

Soma Komur said in a statement that the accident had occurred despite all precautions and would be investigated.