Japan's Nikkei share average gave up most of its morning gains during the afternoon session to close below the key 27,000 level on Monday, as investors fretted about the outlook for China's economy.

Japan's stock benchmark ended the day up 0.31% at 26,974.90. Of the benchmark's 225 components, 133 rose versus 88 that fell, with four flat.

The broader Topix rose 0.28% to 1,887.19.

The Nikkei had started the day brightly, entering the lunch break 1% higher, buoyed by optimism about a slightly less hawkish U.S. Federal Reserve and the potential for a weaker yen to boost earnings as the corporate reporting season picks up pace this week.

However, focus turned increasingly to China amid a deepening selloff in Hong Kong and mainland equities after Chinese President Xi Jinping chose a leadership team at the twice-a-decade Communist Party Congress that suggested a focus on ideology-driven policies, sacrificing economic growth.

That includes the controversial zero-COVID policy, along with the "common prosperity" initiatives that led to the collapse of the property market and the humbling of China's tech giants.

"That should at least slow the pace of a rebound in the Chinese economy," said Masayuki Kichikawa, chief macro strategist at Sumitomo Mitsui Asset Management.

"To the extent that we need to be wary about downside risks for Chinese growth, this will not be helpful to investor sentiment in Japan."

Real estate was the worst performing sector in the Nikkei, tumbling 2.12%.

J.Front Retailing was the biggest decliner, down 3.72%, followed by a 3.56% loss for department store operator Isetan Mitsukoshi Holdings and a 3.28% drop for peer Takashimaya.

Mitsubishi Estate was next, losing 2.6%.

Startup investor SoftBank Group, which is heavily invested in Chinese tech companies, ended 0.43% lower after rising as much as 3.8% earlier in the day.

Chip-related companies finished with most of their strong early gains intact. Tokyo Electron added 2.01% and Advantest advanced 3.09%. (Reporting by Kevin Buckland; Editing by Shailesh Kuber)