The epicentre of the shallow quake was about 40 kilometres (25 miles) southeast of Along.
A strong 6.1-magnitude earthquake struck Arunachal Pradesh early on Wednesday, the US Geological Survey said.
The epicentre of the shallow quake was about 40 kilometres (25 miles) southeast of Along, and 180 kilometres southwest of the state capital Itanagar.
It struck at 1.45 am (2015 GMT Tuesday).
Arunachal Pradesh is home to more than 1.2 million people, according to the state government’s website.
China’s official state news agency Xinhua said the quake was felt in Tibet, which neighbours the state.
Arunachal Pradesh also borders Myanmar and Bhutan. USGS estimated there was a “low likelihood” of casualties and damage from the quake.