Yahoo chief executive Marissa Mayer says the company has made "great progress" despite reporting a loss for the second quarter.

The search and advertising firm reported a net loss of $21.6m in the quarter to 30 June, but said revenue rose 15% to $1.04bn.

In the same period a year ago, it reported a profit of $269.7m.

"Yahoo's transformation continues to make great progress," said Ms Mayer.

The company's boss, who has been at the helm for three years, has been steering it away from advertising tailored to desktop computers towards mobile and video adverts to increase sales.

Revenue from the division that includes mobile, video, native and social advertising was up 60% in the second quarter to nearly $400m.

Yahoo has also developed a mobile search engine called Gemini that she said could deliver "a better, more intuitive experience".

"Mobile has fundamentally changed the search landscape," Ms Mayer said.

Total revenue after deducting fees paid to partner websites was flat at $1.04bn.

Search revenue rose 22%, while revenue from display ads was up by 15%.

Shares fell 1.6% in after-hours trading in New York to $39.10.

The stock is down more than a fifth this year.