Chinese policy-makers are in talks about how to remove Kim Jong-un as leader of North Korea as new satellite images reveal preparations are underway for a sixth nuclear test.

They are also discussing supporting surgical strikes on the rogue state, said the China initiative director of Columbia University's School of International and Public Affairs.

According to the Korea Times, Professor Zhe Sun told a security forum in Washington that the Chinese were debating how best to deal with the North Korean leader.

'Some Chinese scholars and policy makers began to talk about supporting "surgical strikes" and "decapitation" by the U.S. and South Korea as one policy option,' he said.

Satellite images of North Korea's nuclear test site shows activity at all three of its tunnel complexes, fuelling speculation of another test ahead of a key political anniversary next week

Professor Zhe Sun told a security forum in Washington that the Chinese were debating how best to deal with the North Korean leader

'More radical proposals indicate that China should change the leader, send troops across borders and station in DPRK, force DPRK into giving up nuclear and beginning opening up and reforming.'

Analysis of recent satellite images of North Korea's nuclear test site shows activity at all three of its tunnel complexes, fuelling speculation of another test ahead of a key political anniversary next week.

North Korea has already conducted two nuclear tests this year - in January and September - and experts say it is capable of carrying out a third as soon as the order is given. This would be the sixth nuclear experiment since the country started testing in 2006.

Past nuclear tests, and missile launches, have often coincided with special political dates.

Chinese scholars and policy makers are said to be discussing supporting 'surgical strikes' against the North Korean leader (pictured)

North Korea has already conducted two nuclear tests this year - in January and September - and experts say it is capable of carrying out a third as soon as the order is given

The September test took place on the anniversary of North Korea's founding as a state, and the country will celebrate a similar milestone on Monday with the 71st anniversary of the founding of the ruling Workers' Party.

In a posting on its closely-watched 38 North website Friday, the US-Korea Institute at Johns Hopkins University said satellite images dated October 1 showed continuing activity across the Punggye-ri test site in the northeast of the country.

'Activity at the North Portal where the September 9 test occurred, may be for a number of purposes including collecting post-test data, sealing the portal or preparing for another test,' the post said.

It also highlighted movement around the West Portal, as well as the South Portal where excavation stopped in 2012.

'The purpose of this activity is also unclear, although the (South) portal is assumed to be capable of supporting a nuclear test once a decision is made to move forward,' it said.

The yield from September's test was estimated at 10 kilotons - the largest so far and almost twice as much as the device detonated in January

North Korea has been hit by five sets of United Nations sanctions since it first tested a nuclear device in 2006, but has insisted it will continue.

The yield from September's test was estimated at 10 kilotons - the largest so far and almost twice as much as the device detonated in January.

South Korea's Yonhap news agency on Friday quoted an unidentified foreign ministry official who raised the prospect of another test to mark the Workers' Party anniversary next week.