Hong Kong stocks sank again on Monday to extend a painful start to the year as traders grow increasingly worried about the outlook for China's struggling economy.

The Hang Seng Index shed 2.3 percent, or 347 points, to 14,961.

The head of research at Kingston Securities, Dickie Wong, said market sentiment has been dampened by disappointing economic data in China and the sluggish recovery in the mainland property market.

"Overall market sentiment is really sluggish. I don't really see so much upside, or a rebound will happen," Wong said.

"So, the real key is: supportive level for Hang Seng Index would be 14,600. If the Hang Seng Index drops below this point, it'll definitely continue to slide."

The Shanghai Composite Index sank 2.7 percent, or 75 points, at 2,756, and the Shenzhen Composite Index tumbled 4.5 percent, or 75 points, to 1,611. (Additional reporting by AFP)