The Centre has summoned to New Delhi the chief secretaries and DGPs of Assam and Mizoram for a meeting on Wednesday while the restive inter-state border was calm, a day after armed clashes left six dead and over 50 injured, officials said.

Notwithstanding the apparent placidity at the border, leaders from the two sides Tuesday voiced anger over the incident, betraying the brittleness of peace.

Union Home Secretary Ajay Bhalla will chair the meeting to discuss the sudden escalation of violence along the Assam-Mizoram border.

The meeting of the chief secretaries and Directors General of Police is expected to work on a peace formula so there is no repeat of such violence, a home ministry official said in New Delhi.

The two northeastern states are locked in a battle over their boundaries for decades, often culminating in clashes big and small but none like the one witnessed on Monday.

Assam Chief Minister Himanta Biswa Sarma, meanwhile, blew hot and cold, saying he will abide by any law enacted by Parliament that forces it to even cede its land to another state but till then it will not allow even an "inch to be encroached".

BJP general secretary and Lok Sabha MP from the state Dilip Saikia demanded that Mizoram tender an apology to the people of Assam for the death of its police personnel.

"What Mizoram police along with local people did yesterday is condemnable. There was a video showing Mizo people celebrating the killing of Assamese police personnel. I condemn this barbaric attack on Assamese people and police," Saikia told reporters in the national capital and demanded an apology.

Mizoram Information and Public Relations Minister Lalruatkima shot right back and claimed CRPF personnel at the border did not restrain armed police personnel and civilians from Assam from intruding into Mizoram despite the tension.

"The bloody clashes could have been averted had CRPF personnel prevented Assam police from entering Mizoram territory," Lalruatkima told PTI.

Assam chief minister Sarma told reporters in Silchar that his government will move the Supreme Court seeking protection of Innerline Forest Reserve from destruction and encroachment and deploy three commando battalions in Cachar, Karimganj and Hailakandi districts bordering Mizoram to strengthen security.

"It is the responsibility of the Centre to define the boundary and we will abide by it...if tomorrow the Parliament enacts a law by which our land can be given to another state, we will do so but till then we will protect our constitutional boundary," he said after paying floral tributes to the slain personnel.

Assam has declared a three-day state mourning after the incident.

"The dispute is not regarding land but encroachment of reserved forests is the issue. We have no settlements in the forest areas and, if Mizoram can give evidence, we will immediately carry out eviction," he said.

"People have sacrificed their lives but boundary has been protected which we will continue to do at any cost. There is very strong deployment of police inside our border and not an inch of land will be allowed to be encroached," he asserted.

Responding to a question about whether there could be a foreign angle to the border flare-up, he said, his government had taken decisions in the last two months which might have angered "certain non-state vested actors".

He claimed some people who entered India from Myanmar wanted to settle in Assam's Dima Hasao district via Mizoram but his government thwarted the attempts. "Then we hit the drug route through Mizoram and Manipur to Assam," he said.

"Finally, the tabling of the Assam Cattle Protection Bill in the state assembly also created apprehension though we have clarified that transporation to northeastern states will not be affected provided they have valid permit," he added, while explaining the reasons that could have upset the non- state actors.

When asked if the problem could have been resolved as constituents of NEDA, the northeastern version of the NDA, were ruling the two states, Sarma shot back, saying, "This is not a political issue but a long-standing boundary dispute.

Earlier, there were Congress governments in both the states.

Was the problem resolved then?"

Assam's Barak Valley districts of Cachar, Karimganj and Hailakandi share a 164-km border with Mizoram's three districts of Aizawl, Kolasib and Mamit.

Tensions along the border with Mizoram in Cachar and Hailakandi districts of Assam have been escalating since October 2020 with frequent incidents of burning of houses and charges of encroachment of land by both sides.

On October 22, 2020, high-level talks were held under the aegis of the Union Home Ministry where it was decided to maintain the status quo and resolve the dispute through discussions.

Tensions flared up again in February this year and since then hundreds of people have fled their homes near Gallacherra border outpost after two huts were burnt down, an Aizawl report said.

After a lull of few months, a grenade was hurled on an Assam government team visiting the border by unknown attackers from Mizoram on July 10, while two back-to-back explosions were heard from across the border in the wee hours on July 11.

Mizoram was a district of Assam before it was carved out as a union territory in 1971 after years of insurgency and the district borders did not really matter. It became a state in 1987 and border issues cropped up as perceptions over where the boundary should be differed.

While Mizoram wants it to be along the inner line notified in 1875, which Mizo tribals feel is part of their historical homeland, Assam insists it should be defined according to district demarcation done much later.

In an unrelated development but which could give an insight into the Centre's approach to border row among states, the government told the Lok Sabha on Monday that such disputes can "only" be resolved with the cooperation of states involved and the Union government just acts as a facilitator.

"The approach of the central government has consistently been that inter-state disputes can be resolved only with the cooperation of the state governments concerned and that the central government acts only as a facilitator for amicable settlement of the dispute in the spirit of mutual understanding," Minister of State for Home Nityanand Rai said.

Assam is engaged in protracted border disputes with Arunachal Pradesh, Nagaland, Meghalaya and Mizoram.

The Union home ministry, meanwhile, said the Centre is in regular touch with the Assam and Mizoram governments and trying to calm down the situation. CRPF contingents have been deployed in the violence-hit area.