Seoul, Aug 21 : North Korean leader Kim Jong-un has visited a navy unit and inspected a cruise missile test aboard a warship, as South Korea and the US began their annual joint military drills, Pyongyang's state media reported on Monday.

Kim visited the Navy flotilla tasked with defending the east coast and watched the seamen on a patrol ship stage a launching drill of "strategic" cruise missiles, the North's official Korean Central News Agency (KCNA) said, without disclosing the date of his visit.

"At the drill aimed to reconfirm the combat function of the ship and the feature of its missile system and make the seamen skilled at carrying out the attack mission in actual war, the ship rapidly hit target without even an error," Yonhap News Agency quote the KCNA report as saying.

Photos carried by the North Korean state media showed a missile firing from Patrol Ship No. 661, with Kim observing the scene aboard a separate vessel.

Kim vowed to strengthen the North's navy to make it an "all-round and powerful" service group with improved combat efficiency and modern means of surface and underwater offensive and defensive capabilities, the KCNA said.

Meanwhile, South Korea and the US kicked off the annual Ulchi Freedom Shield (UFS) exercise on Monday, featuring various contingency drills, such as the computer simulation-based command post exercise, concurrent field training and Ulchi civil defense drills.

The exercise will run until August 31.

Kim's inspection came amid expectations that North Korea could carry out major provocations, such as the launch of intercontinental ballistic missiles (ICBMs), in a bid to protest the joint military drills.

The North has long denounced the Seoul-Washington military exercises as a rehearsal for an invasion.