A South Korean citizen was executed for drug trafficking in China in the fourth such case in less than six months, the Foreign Ministry confirmed Monday.

The man, identified by his surname Kim, was convicted of smuggling 5 kilograms of methamphetamine into China in April 2012, a senior ministry official told reporters on customary condition of anonymity. A higher court upheld the ruling six months later. He was arrested in May 2010.

Under Chinese law, producing, carrying or selling 50 grams or more of heroin or methamphetamine is punishable by death.

Kim was also believed to have previously been found guilty for smuggling narcotics three times and carrying them one time.

The execution took place on Dec. 30 in Beijing. Seoul lodged a protest for the six-day delay in delivering the information.

“The government regrets that the execution was carried out despite our repeated requests not to do so from the humanitarian and reciprocal points of view,” the ministry said in a statement, referring to growing international calls against capital punishment and a virtual moratorium on executions at home.

“We will continue to strengthen cooperation not only between related authorities here but also with relevant countries to prevent our citizens from being implicated in drug crimes.”

Kim is the fourth South Korean drug smuggler to be executed since August and the fifth since 2001.

Some 20 South Korean citizens are currently on death row in China, mainly convicted of drug trafficking or murder. Many of them have been granted a reprieve, officials said.

China has executed several other foreigners over drug-related crimes in recent years. They include a Japanese and a Pakistani in 2014, a Filipino in 2013, four Filipinos in 2011, four Japanese in 2010 and a Briton in 2009, according to ministry officials.

By Shin Hyon-hee (heeshin@heraldcorp.com)