The river, less than 60 metres wide even in the rainy season, is spanned by a white bridge that was destroyed during the Vietnam War. The bridge and Dongxing were rebuilt from scratch in the '90s, when the mainland economy boomed.

When night falls, Xiao Chong and his gang wait at the river bank for sampans loaded with beef, wild animal meat or redwood. Hastily, they unload the cargo from the boats and transfer it to trucks parked along the river.

Quiet resumes after 2am.

The cross-border trade is said to be the livelihood of 90 per cent of the population on both sides of the river. That could explain why property prices in this tiny city of only 110,000 are as high as those in Guangxi's major centres.

Although the return from the nighttime activity far outweighs that from his day job as a travel agent and tour guide - 1,800 yuan (HK$2,260) a night against 1,200 yuan per month - Xiao Chong decided recently to start a travel firm, anticipating a boom in the market.

The Guangxi government has picked Dongxing as a tourism city for domestic and international tourists. The 850 million yuan International Tourism and Entertainment Centre, officially opened on July 30, is meant to house various tourist services, including visa application, travel agencies, coach parking, catering, entertainment and hotels.

"The Venetian-style building complex is eye-catching at first glance, but most of the buildings are still vacant," a local said.

A recent policy relaxing application requirements for visas for Vietnam has raised demand for tourism services in Dongxing significantly.

A casino run by a Hong Kong businessman across the border is the major attraction in Mong Cai, especially for mainland tourists. However, the rapid growth in the number of mainland tourists heading for the casino prompted Beijing to ban non-Guangxi residents from applying for a visa for Vietnam in Dongxing from 2005.

The ban was lifted this month, so mainland tourists, as well as Hong Kong and Macau residents, can apply for the visa at border control in Dongxing.

The number of visa applicants at the immigration hall in Dongxing reportedly more than doubled in the first few days after the change in the law.

"I am looking for a boost in tourists during the National Day holiday," Xiao Chong said.