SEOUL, Apr. 23 (Reuters) - North Korea carried out its first nuclear counterattack drills to simulate its "nuclear trigger" management system, guided by leader Kim Jong Un, as a clear warning to its enemies, state news agency KCNA said on Tuesday.

North Korea fired several short-range ballistic missiles on Monday toward the sea off its east coast, South Korea's military said.

As part of testing the nationwide nuclear management system, called "nuclear trigger", its artillery forces joined the country's first such drills on Monday in a show of diversified nuclear capabilities and protest against U.S. and South Korean "provocative and invasive" military exercises, KCNA reported.

Kim oversaw the simulation drills involving maneuvering troops in nuclear counterattack posture, and firing artillery with mock nuclear warheads, in case nuclear crisis alerts were issued, according to KCNA.

Kim highly praised the readiness of "the world's best" tactical nuclear attack weapons, expressing satisfaction with the drills, state media said.

The reclusive state is believed to be preparing to launch another spy satellite, after successfully putting a reconnaissance satellite in orbit in November.

North Korea said last week that it had fired a strategic cruise missile to test a large warhead, and a new anti-aircraft missile.