South Korea's top military commander checked the combat readiness of frontline troops on Friday as inter-Korean tensions have flared up in the face of North Korea's continuing provocations.

Joint Chiefs of Staff Chairman Gen. Lee Sun-jin visited the VIII Corps and Navy 1st Fleet earlier in the day to look into their military preparedness, the military said. 

The Army corps is in charge of guarding the eastern part of the heavily militarized border while the Navy fleet defends the East Sea area. 

"North Korea is likely to launch sudden provocations at an unexpected time and place," the four-star general said. He said Pyongyang could also conduct an additional nuclear test or launch a long-range missile.

Other possibilities involve artillery attacks, drone infiltration or terrorist activities in the rear, he noted. 

"In the event of provocations, retaliate powerfully and without hesitation," the JCS chairman stressed to Army servicemen.

During his visit with Navy troops, Lee brought up earlier maritime military clashes with North Korea, and ordered the forces to "safeguard the East Sea at all cost so such tragedies would never be repeated."  

The field inspection came as North Korea continued its bellicose rhetoric against South Korea and the United States.

The communist country launched short- and mid-range missiles and artillery rockets on four occasions this month while upping its military ante.

A day earlier, the North threatened to launch attacks on South Korea's presidential office Cheong Wa Dae.  (Yonhap)