South Africa-focused Petra Diamonds said output rose 25 percent in the first quarter and maintained its full-year target of about 3 million carats, as its key Finsch mine was unaffected by labour strikes.

Petra said it produced 816,735 carats in the quarter ended Sept. 30 up from 654,690 carats a year earlier, helped by its Finsch mine. First quarter revenue rose 27 percent to $65.1 million.

The company said the labour situation at its South African operations had remained stable since the end of the industrial action which began in August.

Petra, which has seven producing mines in South Africa and one in Tanzania, said it maintained its overall outlook for average prices for fiscal 2014 ending June 30.

The company said the diamond prices were weak in the post-summer period but that it expected a firmer market through to calendar year end and in the second half of fiscal 2014.

Petra Diamonds, whose customers are primarily in India, the United States and China, gets most of its production from five mines that it bought from Anglo American Plc's De Beers unit, the world's biggest diamond producer by value. Petra shares were up 0.6 percent at 114.9 pence at 10:14 SA time on the London Stock Exchange.