Rapid Action Battalion (RAB) recovered the weapons in Satchharhi jungles of Habiganj's Chunarughat Upazila from what was once perhaps the headquarters of the now-weakened All Tripura Tiger Force (ATTF).
"Around 200 high explosive anti-tank weapons with as many chargers were recovered in a day-long drive" RAB's Additional Director General (operations) Col Ziaul Ahsan said.
Another official told reporters that the raid was conducted on a tip-off.
The recovery at Satchharhi is perhaps the single biggest case of arms seizure since the 2004 Chittagong arms case.
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The huge cache was found inside bunkers dug in deep holes in the hillock, the official said.
The source of the ammunition will be known after further investigation, he said. No arrests however were made in this connection.
The RAB officials were preparing to conduct the drive for several days in Satchharhi, barely 3 kms from the border with Tripura.
Around 100 RAB personnel participated in the raid. The drive will resume tomorrow, the official said.
Rab dog squad and its bomb disposal team jointly conducted the operation and recovered the arms and ammunition which were in abandoned condition in a bunker in the forest, he added.
The ATTF is now weakened and its chief Ranjit Debbarma is now facing trial in Tripura on charges of murder and abduction.
Debbarma, who is said to be handed over to India by Bangladesh after being arrested in Jan 2013, is very close to United Liberation Front of Assam (ULFA) military wing chief Paresh Barua.
The ULFA and ATTF used to smuggle a huge quantity of Chinese-made weapons through Southeast Asia by sea, land them around Cox's Bazar or Chittagong and take them to rebel bases like Satchharhi, from where they would be smuggled into northeast India.