Myanmar's Ministry of Transport and Communications (MoTC) ordered all mobile phone operators on Friday to suspend internet data in nine townships across Rakhine and neighbouring Chin State.
"As a basis for its request, the MoTC has referenced disturbances of the peace and internet services to coordinate illegal activities," Telenor Myanmar said in a statement.
The decree was made under the Telecommunications Law, hitting all mobile operators for an unspecified period.
Myanmar's army is fighting ethnic Rakhine rebels who want greater autonomy from the central state. The Rakhine are Buddhists and are also fighting in northern Chin state which borders their homeland.
The Rakhine accuse the army of committing abuses - including arbitrary arrests - against them, while the military confirmed it shot dead six Rakhine detainees in late April.
Civilians have been killed in crossfires and shellings, even while taking refuge in monasteries.
Villagers in Rakhine said the mobile data ban had cut them off from the outside world, where few have personal computers and most people share information on the violence through social media.
"We have no internet at all. We use the internet to share information through (messaging app) Viber," Kyaw Soe Moe, head of Inn Din village in Rathedaung told AFP.
Local authorities have also been hit by the blanket shutdown.
A police officer in Mrauk U town, home to Rakhine temples but also the seat of ferocious fighting in recent months, said that communication was being hampered.
"We have to use the phone, SMS and fax to report back to our headquarters. Fighting is still on going here every day," the officer who did not want to be named told AFP.
Rakhine is also home to the remaining Rohingya Muslim population, many confined to squalid camps.
Around 740,000 of the stateless group were driven into Bangladesh in a 2017 army crackdown.
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