North Korea fired 16 short-range rockets from its east coast early Sunday for a second straight day, the Joint Chiefs of Staff said, the latest in a series of provocative launches that are in apparent protest of ongoing joint military drills between Seoul and Washington.

The North fired 30 FROG ground-to-ground rockets from the eastern city of Wonsan, the same test site, early Saturday, without making a pre-announcement for civilian flights or vessels.

The North launched the same type of rockets over two times between 00:52 a.m. and 2:31 a.m. Sunday, which flew about 60 kilometers into the sea, according to the military.

“The military has maintained vigilance against additional launches,” the JCS said.

Pyongyang has fired a spate of Scud ballistic missiles and artillery using multiple rocket launchers from its east coast since late February, in apparent protest against ongoing South Korea-U.S. joint military drills. The communist-state claimed the launches were for the purpose of “self-defense.”

The two-week war game Key Resolve ended in early March, while the two-month field training Foal Eagle runs through April 18.

The North has denounced the joint drills as a rehearsal for invasion, while Seoul and Washington have said they are defensive in nature.

The latest rocket launch came three days before Seoul marks the fourth anniversary of the sinking of the South Korean warship Cheonan in the West Sea. South Korea blamed North Korea for the sinking that killed 46 sailors, but Pyongyang has denied any involvement.

Tensions rose further in 2010 after North Korea unexpectedly shelled the South Korean island of Yeonpyeong, killing two Marines and two civilians, as well as damaging houses and military buildings.

The two Koreas remain technically in a state of war as the 1950-53 Korean War ended in a truce, not a peace treaty. (Yonhap)