South Korean officials say North and South Korea exchanged artillery fire Wednesday in an area near the tense border with North Korea.

Initial reports said three shells were fired on either side and most appear to have landed in the sea short of the border. There was no immediate evidence of damage or injuries.

South Korea's defense ministry said the navy heard three shells fired fireD from the North in what may have been a training exercise. A spokesman said the South returned three shells that landed near the border.

A ministry official was quoted as saying the North Korean shells fell in the same area where North Korea killed four South Koreans in an artillery attack in November.

That attack was mounted in response to a South Korean artillery exercise on Yeonpyeong, a small island hugging the maritime border. The North fired more than 100 artillery shells onto the island, killing two marines and two civilians.

The attack severely damaged relations between the two Koreas, which were already strained over the sinking of a South Korean warship in March 2010.

In the first significant sign of a thaw, senior diplomats held what they described as constructive talks last month on the sidelines of a regional security conference in Bali, Indonesia.

A North Korean delegation later visited New York for additional talks with U.S. officials.