SHANGHAI - US travel booking service Priceline has increased stakes in its Chinese equivalent Ctrip to 12.63 percent in a bid to gain greater exposure to China's booming travel market, Ctrip said over the weekend.

Priceline bought up to 129,200 American Depository Shares of Ctrip each day between Sept 15 to Oct 16 at a price range between $61.8 to $69.6, Ctrip said, citing filings to the Securities and Exchange Commission.

In May, Priceline invested $250 million in Ctrip's convertible bonds and suggested it may acquire more of the company's stake in the open market. Priceline now holds 15 percent of all of Ctrip's outstanding shares, according to Ctrip.

China's online travel market continues to boom, with growing numbers of Chinese booking outbound travel online. Online travel booking is currently less than 20 percent, compared with 44 percent in the United States in 2014, according to research firm PhoCusWright.

The investment will also see greater synergy between Priceline and Ctrip in opening their own hotel resources to each other and boosting Priceline's presence in China.