Chinese President Hu Jintao pledged "unremitting efforts" to maintain peace on the Korean peninsula during talks Monday with his South Korean counterpart after the death of Kim Jong-Il.

Hu met Lee Myung-Bak at the Great Hall of the People in central Beijing on a high-profile visit by the South Korean president set to be dominated by concerns over the leadership transition in nuclear-armed North Korea.

The visit comes as China, Pyongyang's only major ally, and Seoul closely watch the impoverished North amid fears of instability after last month's sudden death of leader Kim.

"To safeguard peace and stability on the Korean peninsula is in the interest of all," the state China Central Television quoted Hu as telling Lee.

"China will remain in contact and consultations with all sides to make unremitting efforts to realise this."

During talks, Lee expressed appreciation for China's efforts to realise the denuclearisation of North Korea as hosts of the six-party talks that also include South Korea, United States, Japan and Russia, the report said.

South Korea's Yonhap news agency, citing a Seoul official, said the two leaders had an "in-depth discussion" on the situation on the Korean peninsula and agreed to "work together" on the thorny issue.

China, which has thrown its support behind Kim's son and successor Kim Jong-Un, said it attached "great importance" to Lee's visit and hoped for a revival of the six-way nuclear talks, which the North walked out on.

South Korea's top nuclear envoy, Lim Sung-Nam, will hold discussions with his Chinese counterpart Wu Dawei during the visit, Yonhap said, citing a South Korean foreign ministry official.

Lee said in a New Year address last week that the divided peninsula is at a turning point after the death of the older Kim, with the possibility of big change and "a window of opportunity" to improve icy relations.

But he vowed to hit back hard against any provocations from the North under its young new chief. Lee also said the nuclear negotiations could resume when Pyongyang halts its atomic activities.

His visit to Beijing comes after Kurt Campbell, the US assistant secretary of state for East Asian and Pacific Affairs, urged Chinese leaders to stress the need for restraint to their allies in the North.

China, North Korea's biggest economic partner, has thrown its support behind the new leader, as it seeks to maintain stability and prevent a flood of refugees spilling across its border.

The North has harshly criticised the South's leaders since Kim Jong-Un was declared "great successor" to his father, threatening unspecified retaliation against Seoul for perceived insults during official mourning for Kim Jong-Il.

During his meetings Lee also said Seoul would soon begin "domestic procedures" that could enable formal negotiations for a free-trade agreement to start in the first half of this year, Yonhap said.

China is South Korea's largest trade partner, with two-way trade worth $188.4 billion in 2010.

The growing number of Chinese boats caught fishing illegally in the Yellow Sea is also likely to be discussed after a Chinese fisherman was accused of fatally stabbing a South Korean coastguard during a raid last month.

The second death of a coastguard at the hands of Chinese fishermen in less than four years sparked widespread anger in the South.

Illegal fishing by Chinese vessels is common in South Korean waters, with at least 475 boats seized last year compared with 370 in 2010.

Lee will also meet Premier Wen Jiabao during his three-day trip.