China rejected allegations Tuesday that a South Korean rights activist was severely tortured while under its custody for questioning, saying the investigation went according to law and his legitimate rights were guaranteed.

The comments from China's foreign ministry represented Beijing's first official reaction to claims that the prominent activist, Kim Young-hwan, was tortured with electric shocks, beating and other abuses during his nearly four-month detention.

Kim was expelled from China and returned home earlier this month.

"In the course of handling this case, the relevant Chinese section conducted an investigation according to law," the ministry said in response to a question from Yonhap News Agency. "China guaranteed the legitimate rights of the South Korean involved in the case."

The ministry also said it conveyed its position to South Korea's government.

Kim and three other activists were arrested in late March on suspicion of endangering China's national security, a serious charge believed to be linked to his campaign to help North Korean defectors hiding in China and to promote democracy in the North.

In an interview with Yonhap on Monday, Kim revealed details of the alleged abuse, claiming that he was deprived of sleep for a week from April 10, and was beaten up badly in the face and given electric shocks during a torture session that lasted for about five to eight hours on the night of April 15.

The case has shown signs of developing into a point of diplomatic friction between the two countries.

South Korea has vowed to take every possible measure to deal with the issue.

(Yonhap News)