At 0150 GMT the Nikkei index was up 1.02% to 23,531.85, led by gains in the industrial sector and the consumer discretionary sector. So far this year the index is up 16.38%.

Japanese shares started brightly in reaction to government data released Friday that showed improvement in China's vast manufacturing sector, suggesting Beijing's stimulus measures are starting to support growth.

Shares extended gains after a separate survey of China's manufacturing sector was revised up to show the fastest growth in almost three years, but an ongoing trade war between the United States and China remains a risk to the outlook.

There were 205 advancers on the Nikkei index against 18 decliners on Monday.

The largest percentage gainers in the index were electrical equipment makers GS Yuasa Corp up 3.57%, followed by Taiyo Yuden Co Ltd gaining 3.28% and Sumitomo Electric Industries Ltd up by 2.97%.

The largest percentage losses in the index were power cable maker Fujikura Ltd down 2.12%, followed by oil refiner Idemitsu Kosan Co Ltd losing 1.47% and Suzuki Motor Corp down by 1.15%.

Some Japanese shares got a boost after reports of robust online sales in the United States on Black Friday last week, when companies offer discounts to mark the start of the year-end shopping season.

Japanese stocks also rose after the yen fell to a six-month low of 109.715 versus the dollar. A weaker yen inflates exporters' earnings when repatriated from overseas.

The Topix index rose 0.88% on Monday to 1,714.30.

The volume of shares traded on the Tokyo Stock Exchange's main board was 0.38 billion, compared to the average of 1.26 billion in the past 30 days.

(Editing by Stephen Coates)

By Stanley White