Seoul/Washington, Aug 18 (IANS): North Korea is believed to have up to 60 nuclear bombs and the world's third-largest stockpile of chemical weapons totalling to 5,000 tonnes, the US Army said in a report.

The US Department of the Army headquarters made the assessment in its report, titled "North Korean tactics", saying Pyongyang is unlikely to give up these weapons to ensure the regime's survival, the Seoul-based Yonhap News Agency reported on Tuesday.

"Estimates for North Korean nuclear weapons range from 20-60 bombs, with the capability to produce six new devices each year," the report said.

The report also showed that Pyongyang is estimated to possess "2,500-5,000 tonnes of chemical weapons of approximately 20 different types, making it the third-largest possessor of chemical agents in the world.

It is "highly likely" that the North Korean military would use chemical artillery shells.

The regime has also done research on biological weapons and possibly weaponized anthrax or smallpox, which could be mounted atop missiles for use against South Korea, the USand Japan, it added.

"Only 1 kilogram of anthrax could kill up to 50,000 people in Seoul," Yonhap News Agency quoted the report as saying.

North Korea is also believed to have secured advanced computer warfare capabilities, which is another key means of coercive diplomacy, according to the report.

Under the Cyber Warfare Guidance Unit, more commonly known as Bureau 121, the North manages more than 6,000 hackers, many of whom are operating in foreign countries, such as Belarus, China, India, Malaysia and Russia, the report added.