SEOUL, South Korea (AFP) — North Korea fired two short range ballistic missiles on Friday, the South's military said, the latest in a blitz of launches that Washington and Seoul have warned could culminate in Kim Jong Un conducting another nuclear test.

The launch comes as South Korea and the United States conclude 12 days of amphibious naval joint military drills, and just ahead of the Monday start of major combined air drills that will involve more than 200 US and South Korean fighter jets.

Such drills infuriate Pyongyang, which sees them as rehearsals for invasion and has repeatedly justified its blitz of missile launches as necessary "countermeasures" to what it deems US aggression.

South Korea's military said it had "detected two ballistic missiles fired from the Tongchon area in Gangwon between 1159 and 1218," it said, referring to a province on North Korea's east coast.

"Our military has increased monitoring and surveillance and is maintaining a full readiness posture in close coordination with the US," Seoul's Joint Chiefs of Staff said in a statement.

Analysts say Pyongyang's confidence that gridlock at the United Nations will protect it from further sanctions has emboldened it to step up its weapons testing.

At a recent UN Security Council meeting to discuss Pyongyang's launch over Japan, North Korea's longtime ally and economic benefactor China blamed Washington for provoking the spate of missile tests.

The Security Council has been divided on responding to Pyongyang's nuclear ambitions for months, with Russia and China on the sympathetic side and the rest of the council pushing for punishment.