China shares were headed for their worst month in over two years on Friday, after confidence in a government-led recovery wavered earlier this week, knocking shares lower.

The Shanghai Composite Index opened 1.4% lower at 3655.67. The smaller Shenzhen Composite fell 1.5% to 2096.02, while the small-cap ChiNext opened 2.1% lower at 2507.26.

China's main stock index is on track to lose 9% this week, and is down 13% month to date, which would make July its worst performing month since June 2013.

In Hong Kong, the Hang Seng Index opened up 0.4%, and an index of Chinese companies listed in the city rose 0.4%. Hong Kong shares are on track to lose 6% this month, marking its worst monthly performance since September, as volatility in China rattled global investors.

Stocks elsewhere in the region were mixed, with the Nikkei Stock Average flat, the S&P ASX 200 was up 0.4% and South Korea's Kospi 0.3% higher. Overnight, U.S. economic output in the second quarter came in slightly slower than expected at an annualized 2.3%, another piece of patchy data that casts uncertainty over the timing of an expected rise in U.S. interest rates.

China shares have been reeling since an 8.5% loss on Monday, the biggest daily decline in more than eight years, when investors dashed for the exits on worries that government-backed funds might wind down market support.

Shanghai is down 28% since its peak in mid-June, despite fresh rhetoric from the securities regulator that it wouldn't pull away from buying shares.

Analysts warned of further volatility in the afternoon trade ahead of Chinese official manufacturing data Saturday. An early gauge of manufacturing last week could throw doubt on the health state-owned enterprises, according to analysts at IG. "This question might see negative trading in the afternoon as investors close out positions to mitigate that possible risk," wrote IG analyst Evan Lucas in a note.

In Japan, shares were flat after disappointing consumer spending data mitigated a better-than-expected inflation reading.

"If household spending continues to be weak, prices can't continue to rise, and the BOJ might have to think about further easing," said JPMorgan Securities Japan economist Masamichi Adachi.

In commodities, a stronger U.S. dollar continues to batter commodities, many of which are priced in the currency and have become more expensive for foreign buyers. Expectations of a rate increase in the U.S. also gives incentive to shift to higher yielding assets, as commodities don't provide any income and cost money to hold. Gold has sank to five-year lows, and is currently trading at roughly flat at $1088.00 a troy ounce in Asian trade.

Concerns about oversupply and weak demand in China, one of the world's biggest commodities consumers, have weighed on oil prices in recent months. The U.S. government will provide a report on oil supply on Friday during the U.S. day. Brent crude, the global oil benchmark, is up five cents to $53.36 in Asian trade.

The commodities-sensitive Australian dollar hit a six-year low of $0.7293 Thursday and was last at $0.7294.

Eleanor Warnock contributed to this article.

Write to Chao Deng at Chao.Deng@wsj.com

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