The UN’s human rights expert for Myanmar has raised alarm over a lethal escalation in hostilities in the country’s Kachin state, warning that civilians had been killed and displaced in recent government bombing.

Amid reports that the military in Myanmar had blocked relief supplies to people displaced by the fighting, Yanghee Lee, the UN’s special rapporteur on human rights in the country, cited accounts of the army using aerial bombings, heavy weapons and artillery fire in civilian areas near the border with China.

“Innocent civilians are being killed and injured, and hundreds of families are now fleeing for their lives,” said Lee, commenting on the displacement of about 5,000 people in recent weeks of conflict, in which civilians have numbered among fatalities.

According to the UN, children, pregnant women, the elderly and people with disabilities are among those displaced.

“What we are seeing in Kachin state over the past few weeks is wholly unacceptable, and must stop immediately,” Lee said.

“Civilians must never be subjected to violence during the course of conflict. All parties must take all necessary measures to ensure their safety and security,” she added.

Lee’s comments followed an earlier warning by the official in March to the Human Rights Council in Geneva that while the world’s attention had been on Rakhine state, scant attention had been given to escalating violence in Kachin, Shan and other conflict-affected areas in Myanmar.

“Any wilful impediment of relief supplies may amount to war crimes under international law,” Lee said, adding that she had received reports that a food convoy organised by the Myanmar Red Cross had been prevented from entering the village of Man Wai late last month. More than 100 civilians have been trapped in the village for three weeks with very limited access to food, medicine and other items needed for survival.

While international attention has been focused on violence that has forced almost 700,000 Rohingya out of Rakhine state into neighbouring Bangladesh since last August, observers have been warning of the risk of mounting ethnic strife across Myanmar’s states, not least in northern Shan and Kachin, which both border China.

The recent displacement does not include the nearly 100,000 people living in camps in both northern Shan and Kachin since a government ceasefire broke down in 2011.

Also raising the alarm has been the International Rescue Committee, whose regional director, Sanna Johnson, said: “The latest wave of violence in the world’s longest running civil war shows no signs of abating.

“We are increasingly concerned for civilians trapped by the fighting in Kachin state, who have already had to endure so much. Our teams are hearing reports that some have been sheltering in forests since being forced to flee … unable to escape ongoing fighting.”

According to Unicef, logistical and security concerns mean only a third of the target population in Kachin have access to basic healthcare.

Local news reports have described clashes continuing in four areas around the towns of Tanai, Phakant, Myitkyina and Injangyang.

Myanmar must hold a “proper investigation” into alleged atrocities against the Rohingya in Rakhine, a UN security council envoy said on Tuesday, after a visit by UN delegates to the country.

