SEOUL, South Korea >> North Korea shot dozens of rounds of artillery onto a populated South Korean island near the countries’ disputed western border Tuesday, and South Korean troops returned fire, military officials said.

South Korea’s YTN television said two people were injured, several houses were on fire and that shells were still falling on Yeonpyeong island. Yonhap News Agency, quoting a military official, said four soldiers were wounded. The reports couldn’t be immediately verified.

YTN said between 1,200 and 1,300 people live in the island, citing an island resident. TV pictures showed black and white smoke rising from the island in the Yellow Sea.

A South Korean Joint Chiefs of Staff official said dozens of rounds of artillery landed on the island and in the sea. The official says South Korea fired back. The official, who spoke on condition of anonymity because of JCS rules, said South Korea’s military is on alert. He had no other details.

The firing comes amid tension over North Korea’s claim that it has a new uranium enrichment facility and just over a month after North Korean leader Kim Jong Il unveiled his youngest son, Kim Jong Un, as his heir apparent.

Tensions between the two Koreas also remain tense after the sinking in March of a South Korean warship in which 46 sailors died. Seoul has blamed a North Korean torpedo, while Pyongyang has denied any responsibility.

The countries’ western maritime boundary has long been a flash point between the two Koreas. The North does not recognize the border that was unilaterally drawn by the United Nations at the close of the 1950-53 Korean War.

North and South Korea have fought three bloody skirmishes near the maritime border in recent years, most recently in November 2009.