Outside Shan state’s Lashio township – home to the military’s northeastern command – internet and phone services were disrupted, hindering humanitarian responses to the fighting, UNOCHA said.
Restrictions on transport and availability of cash were hindering efforts by local humanitarian groups to give out aid, it said.
A further 40,000 people have been displaced by clashes between the military and its opponents in neighbouring Sagaing region and Kachin state since early November, UNOCHA said.
The military has made little comment on the surprise offensive but earlier this week the junta-appointed president warned the country could end up “split into various parts” if the military was unable to “manage” the fighting.
The remoteness of the rugged, jungle-clad region – home to pipelines that supply oil and gas to China – and patchy communications make it difficult to verify casualty numbers.
Beijing, a major junta ally and arms supplier, on Tuesday confirmed there had been Chinese casualties as a result of the clashes in Myanmar.
A foreign ministry spokesperson did not say whether the Chinese were killed or wounded, nor where precisely the incident had taken place.