According to the Press Trust of India news agency, mobs looted police stations when the clashes began, with 3,000 weapons and 600,000 rounds of ammunition missing.
The state is divided along ethnic lines, with rival Meitei and Kuki militias imposing blockades to keep members of rival communities out.
At least 120 people have been killed in the clashes, although many in Manipur believe the number may be higher.
Around 50,000 people have been forced to flee their homes and are taking shelter in relief centers or in neighboring states.
Retaliatory attacks have seen the bombing of homes and places of worship.
According to a report in the India Today news magazine, over 220 churches and 17 Hindu temples had been destroyed by the end of July.