NANNING -- Guangxi Zhuang autonomous region in South China saw its trade with the Association of Southeast Asian Nations grow 21 percent in the first half of the year, local customs authorities said Tuesday.

ASEAN remains the region's largest trade partner, followed by Brazil, said a statement from the customs department of Nanning, the regional capital.

Trade with ASEAN reached $4.75 billion in the first six months, up 20.9 year-on-year and accounting for 36.2 percent of the region's total foreign trade volume, it said.

ASEAN has been Guangxi's largest trade partner for 12 years. China and ASEAN members formed a free trade zone in January 2010.

Last year, trade between Guangxi and ASEAN amounted to $9.56 billion, up 46.6 percent from 2010.