Dominion Diamond Corp said on Wednesday its executive chairman will step down and be replaced by Jim Gowans, a mining industry veteran, who will take over as non-executive chairman no later than April 30.

The Canadian diamond producer, which has been under pressure from an activist shareholder group, also said Josef Vejvoda has been appointed to the board. Vejvoda is a portfolio manager at Toronto-based K2 & Associates, which led the activist group.

The board will continue its "existing search process" to identify an additional independent director to join it, lead director Daniel Jarvis said in a statement.

Gowans was chief executive of De Beers Canada from 2006 to 2010. More recently he was co-president and chief operating officer of Barrick Gold Corp, the world's biggest gold producer.

The activist group, which have been unhappy with Dominion's shareholder returns, revealed on Dec. 21 that it had bought a 5.4 percent stake in the company, which is the world's third biggest diamond producer.

Dominion Chairman Robert Gannicott alluded in the statement to recent "medical challenges". Gannicott returned from medical leave last July but at the time relinquished his role as CEO.