North Korean leader Kim Jong-un has supervised the test-firing of a new surface-to-sea missile and ordered a tighter defense posture near the western maritime border, state media reported Thursday.

North Korea test-launched the new missile, named Padasuri-6, on Wednesday, the Korean Central News Agency said. A day earlier, South Korea's military said the North fired several cruise missiles off the eastern port city of Wonsan.

The KCNA said the missile hit a target after flying over waters in the East Sea for around 1,400 seconds, or 23 minutes and 20 seconds. It did not disclose further details, such as how many missiles were fired.

It marked North Korea's fifth cruise missile launch this year. The provocation came two days before the 82nd birthday of late former leader Kim Jong-il, the father of the current leader Kim Jong-un.

The North's leader ordered a stronger defense posture in waters north of the South Korean border islands of Yeonpyeong and Baengnyeong, saying South Korean warships have frequently violated the North's waters, the KCNA said.

Kim accused the South of sending warships and patrol ships to defend the Northern Limit Line (NLL), the maritime border that the North does not recognize. Kim called the NLL a "ghost line" that has not been recognized by international laws.

"Now is the time to thoroughly defend our maritime sovereignty with an actual exercise of military force, not with any rhetoric or statements," he said.

"If the enemy violates the maritime border that we've recognized, we will regard it as an infringement on our sovereignty and an act of a military provocation," Kim warned.

North Korea does not recognize the NLL, the de facto maritime border in the Yellow Sea, and has long demanded that the line be moved farther south as it was unilaterally drawn by the US-led UN Command after the 1950-53 Korean War.

Waters near the NLL have been a flashpoint between the two Koreas, where three bloody naval skirmishes took place in 1999, 2002 and 2009. In March 2010, Pyongyang torpedoed a South Korean warship in the Yellow Sea, killing 46 sailors.

At a parliamentary meeting in January, the North's leader warned that if South Korea violates even 0.001 millimeter of our territorial land, air or waters, it will be considered a provocation of war.

Last month, North Korea fired hundreds of artillery rounds into waters near the tensely guarded western border, prompting the South Korean military to conduct live-fire drills in response.

North Korea has been dialing up tensions on the Korean Peninsula with weapons tests and bellicose rhetoric this year, including the launches of cruise missiles from sea and land, as well as a solid-fuel hypersonic missile.

On Jan. 24, North Korea test-fired what it called a new strategic cruise missile capable of carrying a nuclear warhead, named Pulhwasal-3-31, for the first time.

Meanwhile, North Korea's Kim visited a key munitions factory, the KCNA said in a separate dispatch, without revealing the time and location.

A photo carried by the Rodong Sinmun, the North's main newspaper, showed Kim touring a factory presumed to be producing artillery shells.

Kim ordered the Second Economic Committee, an organization in charge of the North's munitions industry, to start a new unspecified project, the report said. (Yonhap)