North Korea is likely to undertake provocations in coming weeks as South Korea and the US conduct annual joint military exercises that the communist nation has bristled at, a US think tank said Wednesday.

The two militaries kicked off the annual Foal Eagle maneuvers on Tuesday, a field training exercise involving ground, air and naval forces, which will run through the end of next month.

Separately the allies plan to conduct Key Resolve, a computer-simulated command post exercise, starting March 13.

North Korea has condemned such exercises as a rehearsal for invasion.

"A Beyond Parallel study predicts that military provocations by North Korea are likely during the period of the exercises," Victor Cha, Korea chairman at the Center for Strategic and International Studies, said in a newsletter, referring to the think tank's website devoted to North Korea issues.

"Beyond Parallel found that the 4-8 week window prior to the exercise period is the best indicator of North Korean behavior during exercises. When US-DPRK relations during this window are coded as negative then the exercise period will see a high level of provocations," he said.

The North's test-firing of a newly developed intermediate-range ballistic missile on Feb. 12 and the Feb. 13 killing of Kim Jong-nam, the exiled half brother of North Korean leader Kim Jong-un, "promises a restive DPRK" during the exercises, Cha said. (Yonhap)