The men were convicted in a district court in China's Jilin province, adjacent to North Korea. Trial evidence said they smuggled large amounts of methamphetamine from North Korea into China in 2011 and sold it to drug traffickers.
After a series of stays of execution and the final decision on execution last month by China's highest court, the Seoul government sought clemency for the men. The pleas were rejected on the grounds that equal punishment was appropriate for domestic and foreign drug crimes, a source told South Korea's Yonhap News Agency.
"The South Korean government expresses deep regret over the latest execution of our citizens in China," South Korean Foreign Ministry spokesman Noh Kwang-il said. "The government has repeatedly pleaded for humanitarian consideration through various levels of channels."
Another South Korean awaits execution in China's Shandong province on drug smuggling charges. The two executed Wednesday join one British man, five from the Philippines and one from Pakistan executed in China on drug offenses since 2009.