SHANGHAI, Feb 6 (Reuters) - China stocks rebounded sharply on Tuesday following six sessions of decline, after the country's state fund stepped up efforts to rescue the slumping market and the securities regulator vowed to crack down on malicious short-selling.

China's blue-chip CSI 300 Index jumped 1.8%, and the Shanghai Composite Index climbed 0.8% after six sessions of loss. Both indexes were on course for the biggest daily jump since Jan. 25.

Hong Kong's Hang Seng benchmark rose 2.5%.

The rebound comes after the blue-chip hit five-year lows, and state-backed investors, dubbed the "national team", stepped up buying of blue-chip stock tracking index funds to support the market in recent weeks.

In an obvious effort to lift the market, China state fund Central Huijin Investment said on Tuesday it has expanded its scope of investment in exchange-trade funds (ETFs) and will further increase such investments.

"Thanks to the stepped-up efforts by the national team, their statement and action greatly enhanced market confidence," said Yang Delong, chief economist at First Seafront Fund Management.

Also helping sentiment, China's securities regulator said it would tighten scrutiny of margin financing, malicious short selling and seek to ward off risks involving pledged shares.

In onshore markets, most sectors rose, with shares in healthcare, artificial intelligence, and new energy jumped 4.8%, 3.4% and 2.9%, respectively.

Stocks in the medium-cap CSI 500 and the small-cap CSI 1000 advanced 3.1% and 2.1%, respectively. However, shares in the micro-cap CSI 2000 slumped 4%.

So far on the day, foreign investors bought more than four billion yuan ($555.79 million) of Chinese shares via the Stock Connect, a sixth straight session of net buying.

In Hong Kong, tech giants jumped 4.2% to lead the gains, with shares in Alibaba and Meituan up 6.8% and 4.9%, respectively.

The broad Asian shares edged up thanks to a bounce in China, although investors were cautious after a slide on Wall Street amid diminishing expectations of a near-term Federal Reserve rate cut, which in turn underpinned the dollar. ($1 = 7.1970 Chinese yuan)

(Reporting by Shanghai Newsroom; Editing by Sonali Paul)