Johannesburg - Three South African trade unions declared a dispute with utility Eskom on Thursday after failing to agree on a pay rise and benefits.

"Solidarity, together with NUM and Numsa, declared a dispute with Eskom ... This comes after wage negotiations with the company deadlocked," the Solidarity union said in a statement.

Solidarity has demanded a 12% wage increase while the National Union of Mineworkers (NUM) and the National Union of Metalworkers of South Africa (NUMSA), which also represent workers at the utility, have demanded a 14% hike.

However, Eskom has offered an 8% increase.

"Solidarity has described Eskom's approach to this year's negotiations as obstinate and unaccommodating," the union said.

In addition to the wage raise, the three unions have demanded a R5 000 housing subsidy for workers.

South Africa's power regulator granted Eskom a 31.3% tariff rise last month to help build new power stations.

Eskom, which provides 95% of the country's power, is battling to meet demand in Africa's biggest economy, and provoked public anger from businesses and labour when it asked for the increased tariff.

- Reuters