By Li Hongmei

The Democratic People's Republic of Korea (DPRK) fired a sixth short-range missile into the Sea of Japan on Monday, defying warnings from U.N. chief Ban Ki-moon and South Korea after a flurry of similar tests at the weekend.

The latest firing was confirmed by the South's Joint Chiefs of Staff (JCS), who said it was unclear if Pyongyang was testing guided missiles or rockets from multiple launchers.

"North Korea (i.e. the DPRK) launched two projectiles on Monday - one in the morning and the other in the afternoon," a JCS spokesman said.

In a statement on Monday, the DPRK angrily rejected criticism that the missile exercises were a deliberate attempt to kick off a fresh cycle of tensions.

"Military training ... is the indisputable right of any sovereign nation," the DPRK's Committee for the Peaceful Reunification of Korea said.

"Viciously taking issue with our military's rocket firing training ... is an unacceptable challenge and a wanton provocation," it said.

Pyongyang fired three short-range guided missiles off its east coast on Saturday and another on Sunday.

South Korea had labeled the weekend tests "deplorable," while U.N. chief Ban Ki-moon urged Pyongyang to exercise restraint.

"It is time for them to resume dialogue and lower the tensions," Ban said in Moscow on Sunday.

The DPRK argues that the real provocation is coming from South Korea and the United States, which have carried out a series of small and large-scale joint military drills in recent months.

The joint exercises have included the use of nuclear-capable B2 stealth bombers and, most recently, the participation of the nuclear-powered aircraft carrier USS Nimitz.