Every night for more than a week, unregistered planes have been carrying unknown goods and people between China and its conflict-ravaged neighbour Myanmar – and experts believe they might know why.

The southeast Asian nation – which shares a sprawling border with China to its northeast – is currently effectively cut off from the world as a new military regime cracks down hard on those who opposed its takeover from a democratically elected government in a brutal coup three weeks ago.

Now it appears Beijing is involved in the violence.

Speculation of China's endorsement of the Myanmar coup first circulated earlier this month, when state-affiliated media described the takeover as nothing more than a "cabinet reshuffle".

But as Myanmar braces for a potentially disturbing level of violence in the weeks to come, attention has been drawn to planes flying each night between Yangon International Airport and Kunming in southern China, which the military regime is now "trying very hard to hide".

The Chinese government and Myanmar Airways have claimed the planes are simply carrying seafood exports.

"There have been false information and rumours about China on issues relating to Myanmar," Chinese foreign ministry spokesman Wang Wenbin said last week, when asked if China is sending equipment and IT experts to Myanmar.

But, "the details of the flights in question make that highly unlikely" and suggest China not only knew about the takeover but sent soldiers over the border to assist the army, civil-military professional Susan Hutchinson wrote in a piece for The Strategist.

When the military – the Tatmadaw – took over, international flights were banned, Hutchinson points out, with few flights now using Yangon International Airport.

"But averaging five flights a night, up to three planes have been making trips to Kunming in southern China," she wrote.

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"Two of the planes are painted with Myanmar Airways colours and the other is unmarked. All of them are leased from private firms, so they should be in good working order."

It's clear, Hutchinson added, from the fact the planes' transponders have been turned off, which is a violation of international aviation rules, and the flights not being registered online by Kunming Airport as arrivals, that "whoever has arranged these flights is going to great lengths to hide them".

"The situation in Myanmar suggests two possibilities for what the planes are carrying. One is that they're bringing in Chinese troops and cyber specialists to help the Tatmadaw control access to the information," she wrote.

"The other is that they're increasing the Tatmadaw's weapons stores."

China's position as the fifth largest arms exporter in the world – exporting well over 16.2 billion units of ammunition in the past 15 years – is also telling, Hutchinson said.

"If past behaviour is a predictive of future behaviour, the prospect of violent action against minority groups and other civilians in the country increased drastically when the military took over," she said.

"This is especially the case for the Kachin on Myanmar's northern border with China, and the 600,000 Rohingya remaining in Rakhine State, bordering Bangladesh.

"It is common ahead of large-scale genocidal campaigns or campaigns to violently quell civil disobedience to see a sharp increase in weapons imports."

Hutchinson noted that it wouldn't take "particularly sophisticated weaponry for the Tatmadaw to continue its genocide of the Rohingya, but it would take volume and ammunition", adding that Myanmar has been one of the top three importers from Beijing for the past decade.

"Kunming, in particular, is home to a significant artillery unit, the 63rd Base of the People's Liberation Army Rocket Force, as well as a range of signals intelligence and cyber units, including one focused on operations in Southeast Asia. As a regional hub, the city also has significant storage and logistics facilities and an air base."

With the United Nations Security Council prohibited from getting involved in Myanmar – due to the influences of both China and Russia – it's unclear whether either country "knew what Min Aung Hlaing was planning in the weeks ahead of the coup", Hutchinson said.

But, she added, "the contents of those planes may well tell us what is ahead".