Former South Korean president Roh Tae-woo was admitted to hospital with a bad cough and ended up on the operating table to remove an acupuncture needle from his right lung.

Local media reports said Roh, 78, was released from Seoul National University Hospital on Monday after surgery to remove the 6.5 cm needle.

Doctors are puzzled how the needle ended up in his lung, and acupuncturists say that none of their procedures involved penetrating the lung.

"I can't figure out how the needle got into there," Dr Sung Myung-whun was quoted as telling reporters at the hospital after the operation. "It is a mystery for me, too."

Roh, who served as president from 1988 to 1993, has been in poor health since 2002 when he received surgery for prostate cancer.