Narendra Modi’s political opponents are seizing on a grisly, three-month conflict in India’s north-eastern state of Manipur to challenge the prime minister on a security crisis of national significance they say his government has failed to contain.

Opposition parties, who are sharpening their lines of attack ahead of next year’s general election, say the violence is a threat to national security — a view shared by some analysts who warn it threatens to spill over to neighbouring states in a volatile region.

Members of the newly formed India National Developmental Inclusive Alliance, an opposition umbrella group, accused Modi at the weekend of “brazen indifference” to the violence, which has killed more than 180 people and displaced more than 60,000 since May.