Assam-Mizoram Border Dispute escalated earlier this week.
Amid a long-simmering dispute with Mizoram, six Assam cops were killed in clashes on Monday, triggering fresh tensions and concern over the border row. Both states blame each other for the sudden escalation.
After reports of fresh violence emerged on Monday evening, Chief Ministers of the two states - Assam's Himanta Biswa Sarma and Mizoram's Zoramthanga - urged the central government to intervene.
The issue escalated on Friday when Mizoram Police said they have filed a case, naming the Assam Chief Minister and other officials. The report said Assam police personnel, acting under instructions from Mr Sarma himself, refused to have an "amicable dialogue" with the Mizoram Police on the day of the incident.
Mizoram was earlier a part of Assam and was known as "Lushai Hills". It became a Union territory in 1972 and a state in 1987.
Three districts of Assam - Cachar, Hailakandi and Karimganj - share a 164-km-long boundary with three districts of Mizoram - Aizawl, Kolasib and Mamit. The boundary passes through a forested area and at many points, it is contested by both states.
Assam and Mizoram accuse each other of encroachment.
At the heart of the dispute are two notifications issued during the British rule - in 1875 in 1933 - on demarcation of the boundary between the two states.
The Mizos say they do not accept the 1933 notification, and claim their leaders were not consulted for it.
The first row broke out in 1994, seven years after Mizoram became a state.
The Union government organised several rounds of talks between the two states to resolve the boundary dispute but tensions remained.
A major escalation occurred in October-November 2020. Residents of both states clashed twice and the national highway linking them was blocked for several days.
About 20 shops and houses were torched and over 50 people were injured in the clashes.
At that time too, the states blamed each other.
Following Union Home Minister Amit Shah's intervention, central forces were deployed to maintain peace and end the blockade.
Earlier this month, Chief Secretaries of Assam and Mizoram had met to discuss the boundary dispute. Hours after the meeting, a grenade blast was reported in an area in Mizoram where senior officials from Assam were visiting.
Tensions have peaked after the clashes between the police forces of the states at the contentious border point Lailapur. Assam Chief Minister announced on Twitter that six of the state's police personnel were killed "while defending the constitutional boundary of our state".
Assam Police alleged that people from Mizoram threw stones and attacked officials on the other side.
Lalchamliana, Mizoram's Home Minister, said the state police responded to Assam police officials after they "forcibly crossed" a post manned by the Central Reserve Police Force (CRPF). The CRPF is a "neutral force" deployed by the Centre.
Both the Chief Minister, too, continued to argue and sought Centre's intervention.
Last week, Amit Shah had held closed-door meetings with the Chief Ministers of northeastern states in Shillong and discussed the inter-state disputes.
After the central government intervened again, Mizoram Chief Minister Zoramthanga appeared to calm the situation, saying, "Northeast will always be one".
He also hoped for an "amicable solution" to the boundary dispute.