Anti-junta fighters in Myanmar’s Chin State are trying to gain control of part of the porous border with India, after taking over two military outposts on the mountainous frontier, a rebel commander said, part of a wider offensive against the junta.

Dozens of rebels battled the Myanmar military from dawn to dusk on Monday to overrun two camps next to Mizoram, Chin National Front (CNF) Vice Chairman Sui Khar said. Spokespersons for Myanmar’s military and India’s foreign ministry did not immediately respond to requests for comment.

Myanmar’s generals are facing their biggest test since taking power in a 2021 coup after three ethnic minority forces launched a coordinated offensive in late October, capturing some towns and military posts.

The military-appointed president last week said Myanmar was at risk of breaking apart because of an ineffective response to the rebellion – the most significant fight back since the 2021 coup deposed the democratically elected government of Nobel laureate Aung San Suu Kyi.

The Generals say they are fighting “terrorists”.

The offensive, named by rebels as “Operation 1027” after the date it began, initially made inroads in junta-controlled areas on the border with China in Shan State, where military authorities have lost control of several towns and more than 100 security outposts.

“We are continuing our attacks in northern Shan State,” said Kyaw Naing, a spokesperson for the Myanmar National Democratic Alliance Army, which is part of the operation.

Fighting also erupted on two new fronts this week, in the western states of Rakhine and Chin, which sent thousands of people fleeing to Mizoram.

About 80 rebels mounted attacks on Rihkhawdar and Khawmawi military camps in Chin at around 4 a.m. on Monday, eventually taking control of both outposts after several hours of fighting, Sui Khar said.

Following the rebel attacks, 43 Myanmar soldiers crossed over to Indian and were held by security forces in Mizoram, police official Lalmalsawma Hnamte said.

Some 39 of those troops were flown by Indian forces to a border crossing point in neighbouring Manipur and handed over to Myanmar authorities, a security official said on condition of anonymity as he was not allowed to share details of the incident.

The Home Ministry did not respond to a request for comment.

Sui Khar and the Chin Human Rights Organisation said they believed some of these soldiers may have been involved in atrocities against civilians. They did not elaborate.

Chin rebels will now look to consolidate their control along the India-Myanmar border, where the Myanmar military has two more camps, Sui Khar said.

“We’ll move forward,” he told Reuters, “Our tactic is from the village to the town to the capital.”

Chin State, which had been largely peaceful for years, saw fierce fighting after the 2021 coup by junta leaders with thousands of residents taking up arms, many of them assisted and trained by the CNF.

In part due to close ethnic ties, tens of thousands of people from Myanmar have sought shelter in Mizoram, including ousted Myanmar state and federal lawmakers.