North Korea fired 100 artillery shells into the sea Monday in a live-fire drill near the eastern maritime border with South Korea that followed a recent series of missile tests.

The drill began shortly before midday (0300 GMT) using land artillery units based at the eastern tip of the Demilitarized Zone that bisects the Korean peninsula, the South's Joint Chiefs of Staff (JCS) said.

North Korea fired two short-range missiles into the sea Sunday, Seoul's military said, in an apparent show of anger at an upcoming joint military drill between South Korea and the United States.

North Korea on Saturday condemned a port visit by a U.S. aircraft carrier to the South as a "reckless" act of provocation following proposals by Pyongyang to ease cross-border tensions.

The USS George Washington arrived in the southern port of Busan on Friday for joint military exercises starting next week.

North Korean leader Kim Jong-un has warned the reclusive communist country could become "a bargaining chip for the strong" in a statement at a tactical rocket firing drill, official news agency KCNA reported early Thursday. 

Kim's statement and the report of the drill came a day after North Korea fired what appeared to be two short-range missiles into the sea in the latest of a series of launches interspersed with spurned peace overtures to South Korea.

North Korea on Wednesday fired what appeared to be two short-range missiles into the sea in the latest in a series of launches interspersed with spurned peace overtures to South Korea.

A spokesman for the Joint Chiefs of Staff in Seoul said the two missiles were fired from the western province of Hwanghae into the Sea of Japan (East Sea).

Beijing's claim to almost the whole of the South China Sea is "problematic" and the Asian giant's actions have raised tensions, a senior U.S. official said Tuesday on the eve of high-stakes talks.

China also disputes islands with Japan -- a U.S. security ally that Washington is treaty-bound to defend if attacked -- and officials travelling with Secretary of State John Kerry said they had "heightened concerns" about "the readiness of claimants to utilize military, paramilitary, coastguard forces in furtherance of their claims".

North Korea issued another call Monday for a lowering of military tensions with South Korea, even as leader Kim Jong-Un oversaw firing drills on an island near the sensitive maritime border.

A government statement carried by the official KCNA news agency said it was time to end "reckless hostility and confrontation" and called on Seoul to scrap its annual joint military drills with the United States.

Chinese President Xi Jinping stressed the joint suffering of China and South Korea under Japanese militarism during a speech in Seoul Friday that came days after Tokyo announced a landmark shift in military policy.

"In the first half of the 20th century, Japanese militarists carried out barbarous wars of aggression against China and Korea, swallowing up Korea and occupying half of the Chinese mainland," Xi said in an address at Seoul National University.

The United States offered a tacit approval Thursday to Tokyo's easing of some sanctions on North Korea, saying it can "understand" Japan's efforts to resolve abductions of its nationals.

Japanese Prime Minister Shinzo Abe said his government will revoke some of its unilateral sanctions on Pyongyang as a reward for the secretive state's progress in its pledge to reinvestigate the cases of Japanese citizens snatched in the 1970s and 1980s.

China and South Korea issued a joint call for the denuclearization of the Korean peninsula at a summit in Seoul Thursday that was seen as a pointed snub of nuclear-armed North Korea by Beijing.

In a joint statement after their talks, the Chinese and South Korean presidents, Xi Jinping and Park Geun-Hye, reaffirmed their "firm opposition" to the development of nuclear weapons, but seemed divided on how to best persuade the North to give up its bombs.