Hainan's foreign trade surged 109.2 percent year-on-year in the first quarter, outpacing the national figure as the southern island province speeds up construction of a free trade zone.

Local customs said Wednesday that the province's foreign trade reached 25 billion yuan (about 3.7 billion U.S. dollars) in the first quarter. Exports exceeded 7.8 billion yuan, up 78.7 percent year on year, while imports surged by 126.9 percent to reach 17.1 billion yuan.

The Association of Southeast Asian Nations (ASEAN) continues to be Hainan's top export market. The province's exports to the region hit about 2.8 billion yuan, a 133.2 percent increase.

The United States replaced ASEAN as Hainan's largest source of imports, with imports from the country exceeding 6.2 billion yuan, up 520.9 percent.

Its trade with Belt and Road countries surpassed 7.7 billion yuan, up 40.1 percent.

The province added 183 foreign trade enterprises in the period, marking an increase of 128.8 percent, which means more companies are willing to engage in foreign trade, said Ju Chunmei, an official with Haikou Customs.

A rapid increase in foreign trade is expected to continue in the first half of 2019 as Hainan's free trade zone develops steadily, Ju said.