China will expand its investment in South Asian countries and continue assisting in building infrastructure in the area, a senior official said on Friday.

"Both China and South Asia countries are enjoying a harvest season, benefiting from multilateral cooperation in commerce, trade, culture and infrastructure construction," Vice-Premier Wang Yang said at the opening ceremony of the Second China-South Asia Expo.

The five-day expo in Kunming, Yunnan province, is expected to become a key platform for the province's opening-up.

Last year, trade volume between China and South Asian countries reached $100 billion. Chinese enterprises have invested more than $4 billion in South Asia and achieved a construction contract turnover of about $85 billion.

"The expo is open for the public to browse through mazes of booths promoting a variety of tradable goods mainly from Nepal, Pakistan, India, Laos, Myanmar, Thailand, Vietnam and China," said Gao Shuxun, vice-governor of Yunnan.

Forty-six 46 countries and regions are participating in the expo. More than 700 new indoor booths have been added this year, an increase of 32 percent year-on-year. The outdoor exhibition area has been expanded from 500 square meters in 2013 to 7,500 sq m.

"Smart robots, 3-D printers and other high-tech products will be shown for the first time at the expo. Online ticket-booking with WeChat and mobile apps are also available," Gao said.

The first China-South Asia Science and Technology Ministerial Conference was held on Friday in Kunming.