North Korea said Monday its patience is "limited" after South Korea staged a series of military drills, and accused the United States of fanning tensions by supporting Seoul's shows of force.

Ruling communist party newspaper Rodong Sinmun, quoted by the North's official news agency, said the drills were a "dangerous collusion" between Seoul and Washington that would lead to "destruction".

The South has staged a series of military exercises, including one with the United States, since the North shelled an island near the disputed Yellow Sea border last month and killed four South Koreans, including two civilians.

Pyongyang said it was retaliating for a South Korean firing drill that dropped shells into waters which it claims are North Korean territory.

The first attack on a civilian area in the South since the 1950-53 war sharply heightened tensions.

The South on December 20 staged another drill on Yeonpyeong, backed up by about 20 US troops. The North did not follow through with threats of a new and deadlier attack.

On Thursday last week, in another show of strength, Seoul deployed tanks, artillery and jet fighters in a live-fire exercise on the mainland.

"Despite the dangerous collusion between the US seeking a war of invasion and the South's warmongers, there have been no clashes in the Yellow Sea thanks to our self-restraint and firm determination for peace," said the paper.

"But our patience is limited," it said, denouncing Seoul for relying on Washington for military protection. The United States stations some 28,500 troops in the South.

"The... enemy party that can never sustain its power without the protection of the US is scrambling to harm us by relying on the master, but what awaits them is only destruction," the paper said.