South Korea's major pharmaceutical firms saw their revenues from exports of Active Pharmaceutical Ingredients increase last year, industry sources said Tuesday.

API refers to key chemicals used to produce pharmaceutical drugs.

Yuhan Corp., a major drug company, said its revenue from overseas shipments of API jumped nearly 30 percent on-year to 250 billion won ($220 million) in 2016, company officials said.

Yuhan said its API business also accounts for 19 percent of the company's total revenue worth 1.32 trillion won.

Major demand growth comes from leading global pharmaceutical companies such as Pfizer Inc. which manufacturers drugs for AIDS and high-priced Hepatitis C treatment.

ST Farm, a subsidiary under Dong-A Socio Holdings Co. manufacturing API, also generates 82 percent of its revenue from overseas shipments.

The company currently exports API for anti-virus to the Britain-based pharmaceutical company GlaxoSmithKline Plc. as well as Swiss pharmaceutical giant Novartis.

Chong Kun Dang Bio, an API arm of Chong Kun Dang Pharmaceutical, said 81 percent of its revenue came from overseas markets. (Yonhap)