"Earlier today, AMCU sent an official notice to Sibanye-Stillwater, indicating that it will be embarking on secondary strike action from 22 January 2019. This notice relates to all the platinum operations of Sibanye-Stillwater," it said in a statement. 

AMCU members have been on strike at Sibanye-Stillwater's gold operations since mid-November. Sibanye has declared the strike illegal.

(Reporting by Nqobile Dludla; Editing by Alexander Winning)