Around 4,000 Burmese civilians have been stopped from seeking shelter in neighbouring China by Chinese soldiers after they attempted to flee local fighting, a non-governmental organisation said.

The incident occurred in the country's northern Kachin State on Wednesday, where fighting between the Burmese military and an ethnic armed group has displaced 23,000 people since the outbreak of the conflict several weeks ago, campaign group Fortify Rights said.

"China should provide asylum seekers with sanctuary, not send them into the line of fire," said Matthew Smith, chief executive officer of Fortify Rights.

The organisation also said that Myanmar authorities were restricting humanitarian aid groups from operating in the affected region.

The restrictions were resulting in "avoidable deprivations of food, healthcare, and other humanitarian provisions for displaced communities," Fortify Rights said.

Kachin State has been beset by a conflict since 2011 when government troops broke a 17-year-old ceasefire agreement with the Kachin Independence Army (KIA). More than 100,000 civilians have been displaced since.

Elsewhere in Myanmar, fighting between the military and an ethnic rebel group, Ta'ang National Liberation Army (TNLA), has intensified and the two sides traded blame on Friday over heavy shelling that killed two civilians in an area near the country's northeastern border with China.

IN PICTURES: Displaced in Shan state

The office of the commander-in-chief of the armed forces said TNLA fired heavy weapons at a military outpost in Namhsan Township of Shan State on Thursday, but four stray shells landed in Ho Chaung village around three kilometres away from the outpost.

"Two residents were killed and eight villagers, including three women, injured because of the strayed weapon shells," the statement said.

The dead included a seven-year-old boy who the statement said was injured while playing outside his house and died on the way to hospital.

The rebel group, however, said the shells were fired by the Myanmar army as the ethnic people of the region gathered to celebrate Ta'ang Revolution Day on January 12.

TNLA spokesperson Ta Aik Kyaw told Anadolu Agency that the group attacked the army bases in retaliation for recent assaults on their outposts in the area.

The TNLA and other groups jointly attacked police stations, military outposts and a trade zone in Shan's Muse Township in November.

Several rebel groups had refused to sign the Nationwide Ceasefire Agreement (NCA), a peace deal between Myanmar's previous quasi-civilian government and eight rebels groups in October 2015.

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State Counsellor Aung San Suu Kyi, the de facto leader of the country's first civilian government in more than 50 years, has been calling on rebel groups to join an ongoing peace process by signing the NCA as her administration prepares to hold a second meeting with armed ethnic groups later this month.

On Friday, New York-based Human Right Watch (HRW) said the government has failed to hold the military accountable for persistent human rights violations throughout the country.

In its World Report, HRW said Myanmar's new civilian government has done little to address the military's brutal crackdown on ethnic Rohingya Muslims in western Rakhine State and other abuses against civilians, or to reform laws limiting freedom of expression and assembly rights.