Seoul, South Korea (CNN) -- North Korea fired artillery toward its tense western sea border with South Korea on Tuesday, killing at least one South Korean soldier, the Yonhap news agency reported.
Two civilians and 13 other South Korean military personnel were injured, with three of the soldiers seriously hurt, Yonhap said.
A Ministry of Defense spokesman contradicted the Yonhap report, saying that no deaths had been confirmed and that the military was checking on possible civilian casualties.
At least 200 rounds of artillery hit an inhabited South Korean island in the Yellow Sea after the North started firing about 2:30 p.m. local time, Yonhap said.
South Korea's military responded with 80 rounds of artillery and deployed fighter jets to counter the fire, the report said.
The South Korean army also raised its alert condition, the report said.
Images of plumes of smoke were quickly broadcast on Yonhap television from the island of Yeonpyeong, with some homes on fire. It was not immediately clear how much damage the artillery had done. The island has a large military garrison.
The island has a total of about 1,300 residents, a fisherman who lives on the island told Yonhap.
Some residents started fleeing for the South Korean mainland, which is about 145 kilometers [90 miles] away. Other residents were seeking shelter at schools.
The South Korean government immediately called an emergency meeting of its security ministers, meeting in a bunker under the presidential residence in Seoul.
South Korean President Lee Myung-bak ordered his ministers to take measures against an escalation of the situation, presidential spokeswoman Kim Hee-jung said, according to Yonhap.
"Take a stern response and carefully manage the situation from further escalating," the president said.
The North Korean fire came as the South's military conducted routine drills in waters off the island, which is about 10 kilometers [6 miles] from the North.
The Yellow Sea has been a longstanding flashpoint between the two Koreas, but Tuesday's attack was an escalation in violence.
"Our navy was conducting a maritime exercise near the western sea border today. North Korea has sent a letter of protest over the drill. We're examining a possible link between the protest and the artillery attack," presidential spokeswoman Kim said, according to Yonhap.
The island is part of a small archipelago about 80 kilometers [49 miles] west of the South Korean port of Inchon, which serves Seoul, and is close to the tense Northern Limit Line, the maritime border between the two Koreas in the Yellow Sea.
A South Korean warship, the Cheonan was sunk in the area in March with the loss of 46 lives in a suspected North Korean torpedo attack.
North Korean artillery is extremely difficult to hit, because it is dug into coastal cliffs. Though the North has tested its artillery -- and tested anti-shipping missiles -- it has not fired artillery into South Korean territory in recent years.
One of North Korea's most potent threats is the hundreds of artillery barrels dug in along its demilitarized zone with South Korea and ranged on Seoul.
Yonhap television was covering the attack nonstop in South Korea, forgoing other news Tuesday. Meanwhile, state television in North Korea did not mention the attack.
Journalist Andrew Salmon contributed to this report.
