Osman Orsal / Reuters

Turkish police have fired teargas and water cannon at 800 protesters who were marching from a university in Ankara to the energy ministry to protest about the fatal coal mine explosion that has killed at least 200 miners and left hundreds trapped underground .

Protests against Soma Holdings, the company that owns the coal mine that exploded killing more than 200 people and trapping hundreds more kilometres below ground, have spread across Turkey with many demonstrators staging sit-ins and holding banners.

The development came as prime minister Recep Tayyip Erdogan, who is visiting the scene, told reporters that the death toll of the disaster had risen to 232.

Riot police blocked off the street outside the Istanbul offices of Soma Holdings where a group of people sprayed "Murderers" on the walls and held placards reading: "This building rises on the blood of workers" and "They didn't die beautifully. This is murder not fate".

They were referring to the words of former labour minister Omer Dincer who said that 30 miners who lost their lives in an accident in Zonguldak in 2010 "died beautifully" and Erdogan who claimed their deaths was "fate".

In Istanbul, groups of youths staged "lay-in" demos in Istanbul metro and Taksim Square. They pretended to be dead to demonstrate against Soma Holdings' safety records.

Protesters also gathered in the Istanbul neighbourhood of Besiktas.

Turkish unions called for a nationwide strike to protest at the deaths deaths and press for more safety measures in workplaces.

The ruling AK Party has come under a barrage of criticism. Erdogan's party has been accused of dismissing a parliamentary motion submitted by the opposition Republican People's Party to investigate safety in the Soma mines as recently as 29 April.

Turkish energy minister Taner Yildiz called the Soma fire "the country's deadliest accident ever" as 300 more workers were feared trapped underground. Yildiz added that 787 workers had been in the mine at the time of the blast.

A cold storage warehouse, usually used for food, and freezer trucks were transformed into makeshift morgues.

The government has ordered flags to fly at half-mast and declared three days of national mourning.