HONG KONG — A pro-democracy heckler interrupted a speech by Chinese President Hu Jintao at the swearing-in of Hong Kong's new leader Sunday and tens of thousands of residents marched to protest Chinese rule on the 15th anniversary of the Asian financial hub's return to Beijing's control.

The outpouring of discontent underscored rising tensions between the Communist mainland and the vibrant city of 7 million that was returned to China in 1997 after more than a century of British colonial rule. While much of the discontent revolves around growing economic inequality and stunted democratic development, Hong Kongers are also upset over what they see as arrogant Chinese behavior — wealthy mainlanders taking over retail outlets during flashy Hong Kong shopping trips, for example, or even the choice of language during Sunday's swearing-in ceremony, Beijing-accented Mandarin instead of the Cantonese dialect spoken locally.

In the ceremony, self-made millionaire Leung Chun-ying, 57, became Hong Kong's third chief executive after Donald Tsang and Tung Chee-hwa. He has promised to address Hong Kongers' economic needs, including skyrocketing housing prices, which many blame on deep-pocketed mainland apartment buyers.