After the Nov 23 incident, the ROK and the US staged joint naval drills from Nov 28 to Dec 1 in waters west of the peninsula.

On Dec 3, Japan and the US launched their biggest-ever joint military exercises at bases across Japan and in the air and on waters around them, with the ROK taking part as an observer.

A series of diplomatic moves are also under way this week.

The DPRK's Foreign Minister Pak Ui-chun is visiting Russia, while US Deputy Secretary of State James Steinberg is to visit China to coordiante their stance on the Korean Peninsula.

ROK's chief nuclear envoy is scheduled to visit Russia for talks with his counterpart Alexei Borodavkin.

And New Mexico Governor Bill Richardson will visit the DPRK from Dec 16 to 20 to try to calm tensions.

China has called for an emergency meeting on the crisis between chief delegates to stalled Six-Party Talks on DPRK's nuclear disarmament.

The US, Japan and ROK have reacted coolly, saying the DPRK must first mend ties with the ROK and show seriousness about disarmament.

Russia is the sixth member of the forum.

Zhang Liangui, an expert on Korean affairs at the Party School of the Central Committee of Communist Party of China, said neither the two sides nor the US intend to go into an all-out war - but they are well prepared for it.

"The toughness of the three nations is mainly shown to their own peoples for internal political concerns," said Zhang.

"But once incidents trigger further fire, the situation is possibly out of their control."

Moreover, border clashes have "every possibility to go beyond the partial war they have prepared for to escalate into (full fighting) they would regret to see," Zhang warned.

Jin Canrong, a professor of international studies at the Renmin University of China, warned that ROK-DPRK hostilities have reached such threshold by which even accidental fire across either side of the border could create a dangerous escalation.

Jin said despite criticism from the US, China will continue with its principle of solving the conflicts through peaceful talks "to put out the fire and appeal for stability from all sides".