Thousands of refugees who have fled to China from war-torn northern Myanmar face a humanitarian crisis due to lack of adequate shelter, food, water and healthcare, Human Rights Watch said Tuesday.

The New York-based group accused China of turning back or forcibly repatriating some displaced people from Myanmar's northern Kachin state, where a 17-year ceasefire between the military and armed rebels collapsed last June.

It urged Beijing to let UN agencies deliver emergency aid to the estimated 7,000 to 10,000 ethnic Kachin refugees who have sought refuge in southwestern China since fighting erupted a year ago.

"Both aid workers and refugees are telling us that their resources are running out," Phil Robertson, HRW deputy Asia director, told a news conference in Bangkok.

"We are looking at a real humanitarian crisis for this group. It's a group of refugees in a desperate situation."

China has not provided any aid to the refugees, who are surviving on limited assistance from local and international agencies, and has refused access to the UN refugee agency and other major humanitarian organisations, HRW said.

The conflict between the Kachin Independence Army (KIA) and Myanmar's military has displaced tens of thousands of people, with both sides accused of rights abuses such as the use of child soldiers and landmines.

Myanmar's reformist government has inked ceasefires with several ethnic rebel groups as part of reforms since coming to power last year. But six rounds of talks with the Kachin since November have failed to achieve a breakthrough.

Beijing was long a key ally and backer of the junta that ruled Myanmar for decades, and remains close to the country's military and new authorities, even as Myanmar reaches out for wider international acceptance.

The HRW report -- based on more than 100 interviews with refugees, relief workers, and others -- accused China of failing to meet its its international legal obligations on refugees.

Although displaced Kachin have generally been allowed to enter and stay in China's Yunnan province, HRW said it had documented two instances in which an estimated total of 300 people were ordered to return to Myanmar.

A number of others have been turned away by China at the border, although it is unclear whether they were isolated cases, according to the rights watchdog.

This "put the refugees at grave risk and created a pervasive fear of forced return among the Kachin refugees who remain in Yunnan," HRW said.

Kachin refugees in China meanwhile have been subjected to arbitrary drug testing, resulting in some being sent to "rehabilitation centres" where they are forced to work without pay in "inhuman" conditions, the report said.