Chinese Foreign Minister Yang Jiechi said regional powers should capitalise on the willingness of the parties to discuss restarting the talks, which North Korea formally abandoned in April 2009.

"We're happy to see that there have been some new positive interactions among the parties concerned surrounding the restart of the six-party talks," said Yang at a seminar to mark the sixth anniversary of the talks' only joint statement.

"The parties must seize the opportunities and keep the momentum of the dialogue going."

The South's chief nuclear negotiator Wi Sung-Lac and his North Korean counterpart Ri Yong-Ho will meet in Beijing on Wednesday for their second round of talks in three months aimed at restarting the six-nation negotiations.

Prospects of reviving the dialogue have been clouded by growing tensions on the Korean peninsula, after the South accused the North of two deadly attacks last year.

But the North's disclosure last November of a uranium enrichment plant, which could give it a second way to make atomic weapons, leant urgency to efforts to restart the forum grouping the two Koreas, China, the United States, Japan and Russia.

"As long as we all adhere to the spirit of the September 19 joint statement and engage in candid consultations based on mutual respect, mutual accommodation and mutual understanding, the six-party talks will be resumed, keep going and produce results," Yang said.

The September 19 statement was signed in Beijing in 2005 by the six nations and offered North Korea economic and energy aid and stronger diplomatic ties if it halted its nuclear arms programme.

"Depending on changes to strategic situations, North Korea may possibly carry out provocations of varying forms," the ministry said in a report to parliament.

The drills, it said, began earlier than normal in both the Sea of Japan (East Sea) and the Yellow Sea, where the disputed maritime border has been a frequent flashpoint.

Seoul says a North Korean submarine torpedoed a South Korean warship near the contested Yellow Sea border in March 2010 with the loss of 46 lives.

The North denied involvement in the sinking but killed four people in a bombardment of a South Korean frontier island last November. There were also deadly naval clashes in the Yellow Sea in 1999, 2002 and 2009.

Some analysts believe last year's incidents aimed to burnish the military credentials of Kim Jong-Un, youngest son and heir apparent to leader Kim Jong-Il.

It remains unclear when the son will be formally named as successor but the defence ministry said he is already actively involved in state affairs.

"Kim Jong-Un has consistently involved himself in politics and policymaking," its report said.

A member of parliament's defence committee said separately that while the sub drills have increased, the South's navy failed to detect many of the craft taking part.

Opposition party legislator Shin Hak-Yong, quoted by Yonhap news agency, said there were 50 North Korean submarine drills in the Yellow Sea through the end of August compared to 28 drills over the first eight months of 2010.

But in the first and fourth quarters of last year, the South's patrol boats and frigates detected only about a third of the submarines taking part in drills, he said. The defence ministry declined comment.

In its report, the ministry said South Korea and the United States have agreed to complete by year-end a joint military operational plan to prepare against potential North Korean provocations.

The US stations 28,500 troops in the South. The ministry said the plan would specify different steps in response to varying degrees of provocation.

Defence Minister Kim Kwan-Jin told legislators the allies are also discussing revising an accord which limits the range of the South's ballistic missiles to 300 kilometres (186 miles) as well as their payload weight.

"We're having technical negotiations so that the range will cover the entire Korean peninsula," he said without elaborating.