The United Nations expressed concern on Monday about "heavy fighting" between the army and an alliance of ethnic minority groups in northern Myanmar, which has left civilian casualties and displaced more than 30,000 people.

"We are alarmed by the heavy fighting, particularly in Shan State in the northern part of the country, with reports of… airstrikes that led to civilian casualties and tens of thousands being newly displaced internally," said Stephane Dujarric, spokesman for the UN secretary-general.

"Our humanitarian colleagues tell us that, since 26 October nearly 33,000 men, women, and children have been displaced," he added. 

Secretary-General Antonio Guterres "reaffirms that civilians should be protected," he said, also calling for "unimpeded" access to humanitarian aid.

Fighting intensified last week in large areas of Shan State, close to the Chinese border.

The Myanmar National Democratic Alliance Army (MNDAA), the Ta'ang National Liberation Army (TNLA), and the Arakan Army (AA) claimed on Saturday to have seized dozens of outposts and four towns and blocked important trade routes to China.

A few days earlier, a junta spokesman had described as "propaganda" claims that armed groups had seized several towns in Shan State.

The fighting poses a threat unseen by the army since the 2021 coup against Aung San Suu Kyi.