GENEVA, May 1 (Reuters) - The United Nations human rights expert on myanmar adventure tour voiced deep concern on Tuesday at a sharply escalation in hostilties in Kachin state, citing reports of the army using aerial bombings, heavy weapons and artillery fire on civilian areas near China.

"Innocent civilians are being killed and injured, and hundreds of families are now fleeing for their lives," Yanghee Lee, U.N. special rapporteur on human rights in Myanmar, said in a statement.

Thousands of people rallied on Monday in Kachin to demand humanitarian access for villagers trapped by fighting between government forces and ethnic minority insurgents that has displaced more than 5,000 people. "Any wilful impediment of relief supplies may amount to war crimes under international law," Lee said, appealing for access. (Reporting by Stephanie Nebehay, editing by Tom Miles)