Seoul, Oct 10 : North Korean leader Kim Jong-un inspected an exercise of tactical nuclear operation units held in order to check and assess the "war deterrent and nuclear counterattack capability" in response to recent joint military trainings by South Korea and the US, Pyongyang's state media said on Monday. The drills were conducted from September 25 to October 9 while the South and the US were staging a large-scale combined naval exercise in the waters near the peninsula involving the nuclear-powered Ronald Reagan aircraft carrier, according to the North's official Korean Central News Agency (KCNA). The North's military staged "ballistic missile launching drills under the simulation of loading tactical nuclear warheads", Yonhap News Agency quoted the KCNA as saying. It also held a series of live-fire "striking" exercises, including "super-large" caliber missile firing drills targeting major ports of its enemies on Sunday, with long-range artillery and aviation units mobilized. The KCNA further said Kim made clear that he is not interested in talks with the US and South Korea, vowing to strengthen his regime's nuclear force. "We have no content for dialogue with the enemies and felt no necessity to do so," Kim said, as Pyongyang's state-controlled media carried reports on his public activity for the first time in about a month. The KCNA revealed that the North staged large-scale air-attack drills on Saturday, during which more than 150 warplanes took off simultaneously "for the first time in history". Meanwhile, concerns were growing that North Korea may conduct a nuclear test in the near future, with the South's state intelligence agency saying that it may be slated for between October 16 and November 7. The North conducted a string of key weapon tests, including the launch of an intermediate-range ballistic missile (IRBM) over Japan on October 4. The US soon redeployed the aircraft carrier to the East Sea and had another round of joint naval trainings with South Korea and Japan. /IANS