The National Union of Metalworkers of South Africa (NUMSA) said on Monday it had provided a 48-hour strike notice, in line with labour regulations after mediation efforts failed.

NUMSA sought an across-the-board wage increase of 10%, a housing allowance, and an 80% medical aid contribution from the employer, among other demands.

Africa's biggest steel producer, majority owned by Luxembourg-based ArcelorMittal SA, has only offered 5% across the board, as well as cash incentives, the union said, adding, "We reject this proposal."

ArcelorMittal spokesperson was not immediately available for a comment.

(Reporting by Wendell Roelf; Editing by Bhargav Acharya and Sherry Jacob-Phillips)