South Africa’s National Union of Mineworkers (NUM) signed an agreement on Friday with Gold Fields for a wage increase of 21% over three years, it said on Friday.

The wage increase impacts entry level workers and will come into effect on April 1, NUM general secretary Frans Baleni told reporters. The lowest paid workers will receive 7,000 rand ($583) per month in the first year.

Gold Fields CEO Nick Holland said the wage increases reflected the need to retain and attract skilled workers at its South Deep mine, the only fully mechanized underground gold operation in South Africa.

South Africa’s Solidarity union, which mostly represents skilled workers in the mining sector, demanded a 12% increase from the Chamber of Mines on Friday.

The NUM, which represents 57% of the workforce in the gold sector, said in March it would ask for increases of up to 100% for its lowest paid members in the gold, coal and diamond sectors at wage talks due mid this year.

Gold companies operating in South Africa include AngloGold Ashanti, Africa’s top bullion producer, Harmony Gold and Sibanye Gold.