South Africa's Gold Fields Ltd said on Monday its output for the quarter to end-September fell around eight percent to 993,000 ounces but it said production was on track for a good December quarter.
Gold Fields, the world's fourth biggest gold producer, said its attributable reserves fell by 14.2 million ounces to 64.8 million ounces during the financial year to June.
The mining firm said production at South African mines fell 40,000 ounces to 647,000 ounces and by 45,000 ounces to 346,000 ounces at the group's international operations.
"By the end of September, operations had returned to normal and indications are that production is on track for a good December quarter," the mining group said in a statement.
Gold Fields said some 3-4 percentage points of the 8 percent decline in production was due to a strike by gold miners in the quarter under review.
Shares in Gold Fields were 3.48 percent lower at 92 rand by 0854 GMT while the JSE Securities Exchange's gold mining sector lost 3.3 percent.