Telkom, Africa's biggest fixed-line phone operator, said on Friday its acting chief executive officer will not renew his contract when it expires at the end of March, sending its shares lower.

I can confirm that Mr. Jeffery Hedberg has decided not to renew his contract at the end of March this year, Telkom spokesman Pynee Chetty told Reuters.

South African on-line news site Tech Central earlier reported that Hedberg was due to step down, citing senior sources at the company.

Hedberg decided to leave because he believed the government would not allow him to make necessary sweeping changes at the company, including job cuts, Tech Central said.

South Africa's government is Telkom's largest shareholder.

Hedberg's departure is likely to compound investor concern about the outlook for the troubled company, given other recent resignations by senior management.

Hedberg has been Telkom's acting chief executive since former CEO Reuben September stepped down last year. September was followed by chief financial officer Peter Nelson, whose permanent replacement has still not been found.

A U.S. national with a reputation as a turnaround specialist, Hedberg had been chief of international operations at Germany's Deutsche Telekom.

Hedberg was originally brought in to Telkom to fix its ailing Nigerian phone unit, after he helped right Cell C, South Africa's smallest mobile phone operator.

Shares in Telkom dropped 2.7 percent to 36 rand as of 0833 GMT, underperforming a flat JSE All-share index.