(Corrects Daojia user number in second paragraph)

SHANGHAI, Sept 17 (Reuters) - Chinese e-commerce business JD.com Inc and Macquarie Capital have led a $50 million round of investment into online food delivery operator Daojia, as China's e-commerce firms increasingly look to extend their reach offline.

Daojia, formally called Beijing Shishang Renjia Networks Technology Co Ltd, has close to a million registered users in eight cities around China and partners with around 3,000 restaurants, it said in a statement sent to Reuters on Wednesday.

China's technology firms such as IPO-bound Alibaba Group Holding Ltd (IPO-BABA.N), Tencent Holdings Ltd and JD.com have been looking to tap into the online-to-offline, or "O2O", market to widen their reach with the country's consumers.

"We believe that O2O has excellent potential to become the future of e-commerce," JD.com's vice president of corporate development Bin Chang said in the statement, adding that the restaurant delivery services sector was growing fast.

China's fast food market is estimated to grow around 6 percent a year to hit 960.4 billion yuan ($156 billion) by 2018, according to market research firm Euromonitor.

Daojia's founder and CEO Hao Sun said the firm would use the investment, the latest in a series of fund-raising drives, to boost its technology systems and to expand its reach to 20 to 30 cities around China by 2015. (1 US dollar = 6.1430 Chinese yuan) (Reporting by Adam Jourdan; Editing by Ryan Woo)