BEIJING: More Chinese cities advised residents on Wednesday to avoid unnecessary trips for the upcoming holiday long weekend, adding to COVID policies that are keeping tens of millions of people under lockdown and exacting a growing economic toll.

Nanjing and Wuxi, major cities in eastern China's Jiangsu province, recommended residents not leave town during the Saturday-Monday mid-autumn festival, echoing similar advisories made by other cities this month.

China reported a slight uptick in new cases for Sept. 6 to 1,695 - low by global standards - but its "dynamic zero" COVID policy to stamp out every infection chain means numerous cities have imposed various curbs on movement. 

While successful in keeping case numbers down, the approach is weighing on the economy and fuelling widespread frustration nearly three years into the pandemic.

Chinese authorities have not announced any plan to exit the policy that has all but shut China's borders to international travel.

The latest advisories aimed at curbing COVID's spread come just over a month before Beijing hosts a once-in-five-years congress of the ruling Communist Party, where President Xi Jinping is expected to secure a precedent-breaking third leadership term.

The southwestern city of Chengdu, where most of the 21.2 million residents remained on Wednesday in a lockdown that began last Thursday, has yet to announce a plan to end the strict curbs.

In Beijing, the suburban Yizhuang economic and technological development zone said Communist Party officials must not leave the city unnecessarily during mid-autumn festival or the week-long holiday in early October, while residents of the area were also advised to stay put.

"The whole zone ... must strictly and assiduously implement various tasks for COVID prevention and control, in order to create a safe and stable social environment for the party congress," it said in a statement.

Beijing reported 14 locally transmitted infections for Tuesday, the capital's highest daily count since mid-June. All but two of the infections had been quarantined for medical observation before diagnosis, the city said on Wednesday.

In the latest gloomy barometer for the world's second-largest economy, data released on Wednesday showed exports and imports lost momentum in August, significantly lagging forecasts, as inflation crippled overseas demand and fresh COVID curbs and heatwaves in China disrupted output.