South Korea and the United States held a joint exercise in May to counter North Korea's possible biological attacks, a ruling party lawmaker said Sunday.

Kim Hak-song of the Grand National Party (GNP) said that the anti-biological war drill was held on May 17-27 at the South Korea-U.S. Combined Forces Command and the Korea Institute for Defense Analyst (KIDA), and was attended by senior officials from both countries' related agencies.

It was presided over by the U.S., who tried to arouse Seoul's attention to Pyongyang's biological weapons, which pose threats to peace in Northeast Asia, said Kim. But he claimed that Seoul had opposed the exercise, citing negative economic effects and public anxiety.

The drill was aimed at coping with North Korea's asymmetrical attacks with biological weapons and radiation leakage, according to Kim.

North Korea is believed to have 13 kinds of weaponized stocks of biochemicals such as anthrax, cholera and typhoid.

Political and military heavyweights from the two countries, including Gen. Walter Sharp, then commander of the U.S. Forces in Korea, participated in a seminar held at KIDA on the very last day of the drill, said Kim

"South Korea found that it has been hardly prepared to counter North Korea's biological attacks," said Kim. "The Defense Ministry should come up with measures against biological warfare."

According to a study, a bomb that contains 1 kilogram of anthrax can kill up to 11,000 people in a city with a population density of 14,500 per square kilometer. Seoul's density reached 17,240 per square kilometer last year. (Yonhap News)