Nigeria is seeking about $2-billion in back taxes from MTN Group, another curve ball directed at Africa’s biggest wireless carrier that’s come to light less than a week after it was ordered to refund $8.1-billion in “illegally” repatriated funds.

China is exploring a merger between two of the nation’s three wireless carriers to speed up the development of 5G mobile services amid a race with the US over the technology, according to people familiar with the matter.