By Poppy McPherson and Devjyot Ghoshal
BANGKOK (Reuters) - A rebel alliance has overrun parts of northern Myanmar, including areas bordering China, with resistance to the military junta notching its most significant win since the 2021 coup, according to a rebel commander, diplomats and analysts.
The fiercest fighting has been near Myanmar's border with China in northern Shan state where three powerful ethnic armed groups have combined to lead an offensive that has taken multiple towns and military outposts in recent weeks.
Myanmar's military-appointed president said on Thursday the country was at risk of breaking apart due to the failure to deal with the insurgency more effectively.
Alarmed by its neighbour's deteriorating situation, China's foreign ministry said on Friday that Beijing will ensure security and stability at its border with Myanmar and urged all parties there to stop fighting immediately.
Anti-junta fighters operating with "unprecedented coordination" have overrun 100 military outposts and the junta stands to lose control of key border crossings that account for some 40% of cross-border trade and a vital tax revenue source, the United States Institute of Peace think-tank said.
Around 50,000 people have been displaced in Shan, where artillery shelling and airstrikes are continuing, and some have crossed into China, the United Nations said on Friday.
"It is very significant," said one diplomat with knowledge of the assault named by opposition groups as "Operation 1027", after the date it started.
"This is the weakest the Tatmadaw has been since the coup," the diplomat said, referring to Myanmar's military and asking not to be named. Two other diplomats agreed with that assessment.
A junta spokesman did not respond to requests for comment.
Maung Saungkha, leader of the Bamar People's Liberation Army, which contributed troops to the offensive, told Reuters the rebel alliance had spent more than a year preparing to take on the better-armed military.
The operation was "the biggest and most successful of the Spring Revolution", he said, referring to the popular uprising against the junta that ousted a democratically elected government led by Nobel laureate Aung San Suu Kyi in February 2021.
Resistance groups are working closely to batter the already stretched military, said an adviser to Myanmar's parallel civilian administration, known as the National Unity Government, which has backed separate assaults on towns in Sagaing division.
"This opportunity will never ever come back," said the adviser, who declined to be named.
CHINA'S SHADOW
So far, rebel troops have faced unexpectedly weak opposition from the military, according to analysts and resistance leaders who spoke to local media.
The offensive puts further pressure on a military leadership already facing biting economic sanctions, a foreign exchange shortage and a corruption crisis that has ensnared several of junta leader Min Aung Hlaing's allies, the diplomats said.
Myanmar's relationship with China has also been strained over border issues and the latest offensive, led by the "Brotherhood Alliance" comprising the Arakan Army, Myanmar National Democratic Alliance Army and the Ta'ang National Liberation Army, could not have been carried out if Beijing had opposed it, the diplomats said.
Beijing has in recent months been putting pressure on Myanmar to crack down on criminal syndicates running massive telecoms and other online scams from the border areas.
In a statement announcing the operation, the alliance said they intended to remove those enclaves, which they said were protected by the junta.
But China, which seeks to protect major economic investments in the area, has also called for a ceasefire and confirmed this week that there had been Chinese casualties because of firing from the Myanmar fighting spilling over.
While the junta has been weakened, the diplomats said the possibility of an imminent collapse of the armed forces was remote, though they could lose more territory.
"If the regime is able to mount a decisive response, it will likely be able to reopen the trade routes to China," said Richard Horsey, senior Myanmar adviser at International Crisis Group.
"If not, this will be seen as a sign of historic weakness."