Shares in Randgold Resources have fallen 4% after the mining company warned political tension in the Ivory Coast would hit its gold production.
Randgold said its Tongon mine was operating, but on a "curtailed basis".
At least 173 people have been killed in the Ivory Coast following last month's disputed election.
Randgold now expects to produce about 35,000 ounces of gold this year.
A second mill had been delayed because delivery of components had been held up in the Abidjan port and by shipping delays caused by the political crisis.
The company also said its fourth-quarter performance would be affected by a "below-target" contribution from its Loulo complex in Mali.
"We knew that 2010 was going to be a challenging year and the fourth quarter is turning out to be even tougher than anticipated," chief executive Mark Bristow said.
Randgold shares fell 235p to 5,320p in morning trading.