De Beers said that output in the first half of this year rose 12 percent on the same period last year to 16 million carats.
The miner said that the rise was mostly a result of improvements at the Debswana operations in Botswana and De Beers Consolidated Mines in South Africa.
De Beers guidance for output in 2014 was increased to 31-32 million carats from 30-32 million carats previously.
Overall, sales rose by 15 percent to $3.8 billion, of which rough diamond sales were also 15 percent higher at $3.5 billion.
The firm said this was a reflection of "diamantaires’ restocking after a successful selling season and a reasonably positive outlook for polished diamonds in the key markets of the US, China and India".
Looking ahead to the rest of this year, De Beers said: "We see global growth in demand for diamond jewelry of between 4-5 percent in 2014, driven primarily by the key markets of the US and China.
"We also expect to see some recovery in India as positive sentiment returns to the market following the result of the recent elections.
"The fundamentals of the industry remain strong, as growing demand will continue to outpace production. With positions across the value chain, De Beers is well-positioned for growth."
The firm described rough diamond demand as "robust" in the first of this year, "reflecting a positive outlook for polished diamonds in De Beers’ key markets of the US, China and India. This contrasted with the first half of 2013, when encouraging growth in the US was not matched in India (where demand was weak). Stronger year-on-year consumer demand between Thanksgiving and Chinese New Year – the key selling season – resulted in higher levels of retailer restocking during the first half of 2014 than in the same period last year".
"The seasonal nature of polished diamond consumption means that De Beers’ annual performance is generally more heavily weighted towards the first six months, reflecting normal restocking by midstream diamantaires after the key selling season. While stocking levels increase as the end of the year approaches, this is offset by manufacturing slowdowns that typically impact upon rough demand in the second half. It is expected that this trend will continue this year."
Meanwhile, De Beers will continue to "invest for growth", making good progress on three projects in South Africa (the Venetia underground mine), Botswana (the Jwaneng Cut-8) and Canada (the Gahcho Kue joint venture).
In addition, there had been a "good performance" from its two diamond brands, with Forevermark now available in more than 1,400 jewelry stores in 29 countries. Forevermark launched in Turkey in H1 and announced plans to launch in the UK & Ireland later this year.