However, the DPRK's military said in a statement issued late Tuesday that the Korean People's Army (KPA) countered the South Korean artillery firing on Tuesday afternoon, according to Pyongyang's official news agency KCNA.

Smoke rises from South Korean Yeonpyeong Island after being hit by dozens of artillery shells fired by the Democratic People's Republic of Korea (DPRK) on November 23, 2010. [Xinhua]

South Korean troops fired into the waters of DPRK with dozens of shells at 1 p.m. local time (0400 GMT), and the KPA responded immediately to the South Korean military provocation with "determined military measures", it said.

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The clash came at a time when South Korea is engaged in massive annual military exercises involving some 70,000 troops, launched Monday and scheduled to last through Nov. 30.

Some interpret the firing as a show of protest by Pyongyang against the ongoing annual military exercises. The DPRK has sent a message earlier to the South denouncing the drills for potentially targeting it.

South Korea and the DPRK have remained at odds on the so-called NLL, which was fixed unilaterally by the U.S.-led United Nations Command after the 1950-1953 Korean War. South Korea holds the NLL as the de-facto western inter-Korean border, but the DPRK rejected the NLL and only recognized the demarcation line it drew in 1999, which was further south of the NLL.

Chinese foreign ministry spokesman Hong Lei said at a regular briefing Tuesday in Beijing that China had taken note of reports about an exchange of fire between South Korea and the DPRK, urging related sides to do things conducive to peace and stability in the Korean Peninsula.

The spokesman also urged the parties concerned to keep calm and restraint, and to make joint efforts for the peace and stability on the peninsula.