SEOUL: North Korean leader Kim Jong-Il may have left for China on Thursday in what would be his second trip there this year, a South Korean official said.

"Judging from circumstances, Chairman Kim might have left for China early Thursday morning," a senior official told AFP on condition of anonimity.

The apparent trip comes amid increasing speculation about Kim`s successor and efforts by Beijing to revive international efforts on North Korea`s nuclear disarmament.

Yonhap news agency quoted an unidentified senior official as saying that "signs have been detected" that Kim made the visit on a special train.

"We are still trying to grasp his exact destination and purpose of the visit," Yonhap quoted the official as saying.

In May, Kim made a five-day trip to China, where he met President Hu Jintao.

Pyongyang and Beijing have made it a rule not to confirm Kim`s trips to China until he returns home.

Thursday`s apparent visit comes ahead of a crucial North Korean party meeting next month to elect leaders, including, analysts say, Kim Jong-Il`s youngest son and presumed political heir, Kim Jong-Un.

Speculation about succession in North Korea has intensified since Kim Jong-Il, now 68, suffered a stroke in August 2008, but he has since recovered sufficiently to work.

Beijing has been stepping up efforts to resume six-party talks on disarming the North amid simmering tensions over the sinking of a South Korean warship in March, for which the North was blamed.

BDST: 1025 HRS, August 26, 2010