India will deploy a "neutral force" at the frontier of two states in its north-east, after their long-running border dispute escalated into a deadly showdown, officials said Thursday.

The July 26 clash on the border between Assam and Mizoram left six police officers dead and dozens injured, in a major embarrassment to the central government of Prime Minister Narendra Modi.

In a joint statement released Thursday, the governments of both states said a "neutral force" would be deployed by the Indian government in disputed areas.

"For this purpose, both the states shall not send their respective forest and police forces for patrolling, domination, enforcement or for fresh deployment to any of the areas where confrontation and conflict has taken place", the statement read.

The governments of both states said a "neutral force" would be deployed by the Indian government in disputed areas
The governments of both states said a "neutral force" would be deployed by the Indian government in disputed areas AFP / -

Mizoram was part of Assam until 1972 and became a state in its own right in 1987.

The two states have been wrangling over their border for decades, but such deadly escalations are rare.

The government of Mizoram Thursday also expressed regret -- for the first time since the clashes -- over the death of the six police from Assam.

Last week, the chief ministers of both states tweeted that they would seek an amicable approach to the dispute.

Assam chief minister Himanta Biswa Sarma belongs to Modi's ruling Bharatiya Janata Party while Mizoram chief minister Zoramthanga heads the Mizo National Front -- an ally of the ruling BJP alliance.