Shares in Asia Pacific were mixed on Monday, with Japan stocks leading gains among the region’s major markets as investors monitored political developments in the country.

Mainland Chinese stocks shed earlier gains to slip on the day, with the Shanghai composite down 0.24% to about 3,395.68 while the Shenzhen component shed 0.672% to around 13,758.23. Hong Kong’s Hang Seng index was 0.13% lower, as of its final hour of trading.

China announced Monday that manufacturing activity expanded in August. The official manufacturing Purchasing Managers’ Index (PMI) for that month came in at 51.0, according to the National Bureau of Statistics. That was below expectations of a reading of 51.2 by analysts in a Reuters poll.

PMI readings above 50 signify expansion while those below that mark represent contraction. The readings are sequential and indicate on-month expansion or contraction. Chinese economic data has been watched by investors for clues on the state of the country’s recovery from the coronavirus pandemic.

In Japan, the Nikkei 225 gained 1.12% to close at 23,139.76 while the Topix index advanced 0.83% to end its trading day at 1,618.18, after losses on Friday as longstanding Prime Minister Shinzo Abe announced a surprise resignation on Friday due to health reasons. Developments in Japanese politics continued to be watched by investors on Monday, as the search for the country’s new prime minister continues.

The Japanese yen traded at 105.69 per dollar, after strengthening sharply from levels above 106.5 against the greenback late last week.

Meanwhile, South Korea’s Kospi fell 1.17% to close at 2,326.17. The S&P/ASX 200 in Australia dipped 0.22% to finish its trading day at 6,060.50.

Overall, the MSCI Asia ex-Japan index slipped 0.72%.

Shares of Japanese trading firms Mitubishi Corp., Itochu Corp., Marubeni Corp., Mitsui & Co. and Sumitomo Corp. soared on Monday after Warren Buffett announced that his firm Berkshire Hathaway has acquired a slightly more than 5% stake in the companies.

Shares of Mitsubishi jumped 7.72% while Itochu gained 4.19%. Marubeni soared 9.48% and Mitsui gained 7.35%, Sumitomo rose 9.09%.

“The Japanese trading companies are the premier venture capital firms of Japan,” Jesper Koll, senior adviser at Wisdomtree Investments, told CNBC’s “Street Signs” Monday. “What Warren Buffett is buying is incredible diversification of new technology as well as also a hedge on global commodity prices because … the big Japanese trading companies are huge in terms of the global commodities flow.” 

The situation surrounding the ongoing coronavirus pandemic will also likely be watched by investors, with data from Johns Hopkins University showing the number of reported Covid-19 cases worldwide surpassing 25 million. India, among the countries with the highest number of reported virus cases, recently registered the biggest single-day spike globally since the pandemic began, according to the Associated Press.

The U.S. dollar index, which tracks the greenback against a basket of its peers, was last at 92.32 after seeing levels above 93.2 last week.

The Australian dollar changed hmands at $0.7351 after rising from levels below $0.726 last week.

Oil prices were higher in the afternoon of Asian trading hours, with international benchmark Brent crude futures up 1.31% to $46.41 per barrel. U.S. crude futures added 0.88% to $43.35 per barrel.

— CNBC’s Huileng Tan contributed to this report.