China works to ease North-South Korea tension
China's Foreign Ministry has begun working to ease tensions on the Korean peninsula, holding a series of talks with Washington, Seoul and Pyongyang.
Officials said their priority was to avoid a recurrence of Tuesday's violence, which saw North Korea fire artillery shells at a southern island.
The South responded with its own fire, and announced joint military exercises with US forces would begin on Sunday.
Pyongyang said the drills were pushing the region to "the brink of war".
The US and other powers have repeatedly urged Beijing - Pyongyang's only ally - to use its influence to defuse the crisis.
On Friday, China's Foreign Minister Yang Jiechi met the North's ambassador in person, and spoke on the phone to his US and South Korean counterparts, according to a statement carried by the state-run Xinhua news agency.
"The top priority now is to keep the situation under control and to ensure such events do not happen again," the statement said.
Few details of the conversations were released, and the US state department has not yet commented.
At least four South Koreans died on Tuesday when the North shelled the Southern island of Yeonpyeong.
The incident led to the South replacing its defence minister and evacuating most of the island's civilian population.
Another panic was sparked briefly on Friday afternoon when artillery fire was heard near the island, sending people running for shelters.
But the South's military later said the noises appeared to be a routine military exercise by the North.
The top US commander in South Korea, General Walter Sharp, was visiting Yeonpyeong during the brief alert.
Tuesday's barrage of shells was one of the North's most belligerent actions since the end of the 1950-53 war, which concluded without a peace treaty.
North Korea: Timeline 2010
26 March: South Korean warship, Cheonan, sinks, killing 46 sailors
20 May: Panel says a North Korean torpedo sank the ship; Pyongyang denies involvement
July-September: South Korea and US hold military exercises; US places more sanctions on Pyongyang
29 September: North holds rare party congress seen as part of father-to-son succession move
29 October: Troops from North and South Korea exchange fire across the land border
12 November: North Korea shows US scientist new - undeclared - uranium enrichment facility
23 November: North shells island of Yeonpyeong, killing at least four South Koreans
Pyongyang blamed the South for provoking the shelling by holding military exercises close to Yeonpyeong.
The North's official KCNA news agency later warned against the planned military exercises on the weekend.
"The situation on the Korean Peninsula is inching closer to the brink of war due to the reckless plan of those trigger-happy elements to stage again war exercises targeted against the [North]," a KCNA report stated.
The forthcoming four-day US-South Korea naval manoeuvres were organised well ahead of this week's attack, but they have angered both North Korea and China.
Beijing has warned against any infractions into its exclusive economic zone, which extends 320km (200 miles) from China's coast.
But the Pentagon insisted that China was kept informed about the naval exercises, and insisted that they were not directed at China.
"As with previous exercises in this series, these operations are defensive in nature and designed to strengthen deterrence against North Korea," the Pentagon said.
Meanwhile, South Korea has increased troop numbers on Yeonpyeong and says it will change its rules of engagement to allow it to respond more forcefully to similar incidents.
The cabinet decided that the old rules of engagement gave too much emphasis to preventing a military incident escalating.
A presidential spokesman said the South would implement different levels of response in the future, depending on whether the North attacked military or civilian targets.
This week's tension comes as the North is undergoing an apparent transition of power from leader Kim Jong-il to his young son Kim Jong-un.