The latest clashes are another blow to civilian leader Aung San Suu Kyi's hopes to forge a nationwide peace agreement after years of war in Myanmar's many ethnic minority border regions.
Locals in the town of Muse, a notorious hotbed of smuggling, reported that fighting broke out since early morning.
"People from (the) border check point are now fleeing to Muse town because of heavy fighting but we do not know which groups are fighting yet," Aye Aye, a resident in Muse town told AFP.
Fighting between the Myanmar military and Kachin Independence Army (KIA), which reignited in 2011 after the collapse of a 17-year ceasefire, has displaced around 100,000 people and spilled into parts of neighbouring Shan state.
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Muse lies in the north of Shan, not far from Kachin, and is separated from China by a river.
Suu Kyi has made brokering peace with the patchwork of armed minorities fighting the state a priority.
In September renewed clashes broke out in southern Karen state between the military and rebels while the northern half of western Rakhine is currently under a military lockdown after a string of deadly attacks against border posts last month.
More than 30,000 people have been displaced and at least 70 people have been killed in the latest fighting in Rakhine.
Myanmar's military have a long history of rights abuses that has fostered a deep mistrust among ethnic minorities of the central government.