South Korea's independent Hankyoreh daily quoted a source in Dandong as saying that a security alert has been issued in the city for three days between Wednesday and Friday.

Dandong, linked by a river bridge to North Korea's border town of Shinuiju, is the normal point of entry when Kim visits China by rail. He is known to shun flights.

"Chinese security authorities there were put on alert for three days from Wednesday through to Friday," the source said.

"This might be a signal that Kim Jong-Il's visit to China might be imminent," the source was quoted as saying.

South Korean officials declined to comment on the news report. "We are not in a position to comment," a spokesman for the Unification Ministry said.

Speculation about a possible visit has been brewing since mid-August, amid efforts to revive six-nation talks on North Korea's nuclear program involving China, the two Koreas, the United States, Russia and Japan.

But China said last week it had not made any arrangements for a visit by the reclusive leader.

If confirmed, it would be his first visit to China since January.

Kim is known to have visited China four times since 2000. Each time, neither nation acknowledged the trip until after he returned home.

North Korea sparked regional concern and international condemnation in July for test-firing seven missiles. There have also been media reports that it is considering a nuclear weapons test.

The United States has stepped up pressure on China to take stronger action over the missiles and to urge North Korea to return to the six-nation talks.

Pyongyang says it will not return to the forum unless US financial sanctions against it are removed, warning it would take "all necessary counter-measures."

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