SEOUL, South Korea - North and South Korea fired hundreds of shells into the sea today along a disputed demarcation line in a display of firepower and pique that sent villagers on nearby islands fleeing into bomb shelters.

North Korea did take the unusual step of issuing a warning that it would have a live fire drill off its coast before launching around 500 artillery shells over a three hour period into the Yellow Sea. About 100 shells landed south of the Northern Limit Line (NLL) which the South claims as its maritime border. South Korea responded with 300 artillery shells, but they were measured to land below the sea boundary within South Korean territory, according to Kim Min-suk, spokesman for the South's Defense Ministry.

Residents of five South Korean islands in that area were evacuated into shelters.

Raising tensions at this time of the year has been routine during which U.S. and South Korean forces carry out annual military exercises. Pyongyang as repeatedly expressed discontent claiming that the drills pose a national security threat. In protest, it has regularly conducted live fire drills and test-fired missiles.

In Washington, White House spokesman Jonathan Lalley called North Korea's actions "dangerous and provocative" and said they would further aggravate tensions in the region.

The poorly marked western sea boundary has been the scene of several bloody naval skirmishes between the Koreas in recent years. In March 2010, a South Korean warship sank in the area following a torpedo attack blamed on Pyongyang that left 46 sailors dead. North Korea denies responsibility for the sinking. In November 2010, a North Korean artillery bombardment killed four South Koreans on Yeonpyeong.

"The boneheads appear to have completely forgotten the fact that Yeonpyeong island was smashed by our military's bolt of lightning a few years ago," a North Korean military official, Yun Jong Bum, said Monday, according to the North's official Korean Central News Agency.

The bombardment came a day after North Korea warned that it could carry out "a new kind" of nuclear test, but Seoul sees no sign of any imminent nuclear tests.

The Associated Press contributed to this report

U.S. Marines from the 3rd Marine Expeditionary Force landing team, deployed from Okinawa, Japan, participate in the U.S. and South Korean Marines joint landing operation at Pohang's shore on March 31, 2014 in Pohang, South Korea. Chung Sung-Jun/Getty Images