South African coal miners began a strike after wage talks collapsed, disrupting the sector that produces the country’s electricity and exports coal to Europe and Asia, Reuters reported.

The National Union of Mineworkers (NUM), which organised the strike, said that about 30,000 workers could take part.

Two smaller unions which mostly represent skilled workers and supervisors accepted the coal companies’ offers last week. NUM’s arch rival, the Association of Mineworkers and Construction Union (AMCU), has not accepted the offer but its membership levels are small.

‘We took the decision to strike because we reached a deadlock,’ NUM spokesman Livhuwani Mammburu told AFP.

The NUM is demanding a 14% increase for its miners, artisans and officials, and a 13% to 14% increase for the industry’s lowest paid workers.

After over three months of negotiations, the industry bosses have come to the table with an offer of only about half the requested wage rises. ‘Striking is the only way for the workers to express their dissatisfaction with these offers,’ said Mammburu.

According to the Chamber of Mines, South Africa’s coal industry employs about 90,000 people.