By Subir Bhaumik BBC News, Calcutta

Cannabis is grown by farmers in the tribal areas (pic: David Mayum)

Police have seized two trucks loaded with about 15 tonnes of cannabis in Dimapur in India's north-eastern state of Nagaland.

The trucks were being escorted by a commander of the separatist National Socialist Council of Nagaland (NSCN).

The commander, Phungti Jobson, and three other suspected smugglers were arrested, senior police officials said.

The NSCN has a ceasefire with the government and so its vehicles are rarely checked.

Mr Jobson and NSCN leaders have not commented on the arrests. The drivers of the trucks fled.

Biggest haul

"The cannabis was neatly packed in 50 kg cartons, wrapped in plastic bags and concealed under a consignment of dry fish," said Dimapur police superintendent, Bidhu Sekhar.

The trucks had come from Senapati district in the neighbouring state of Manipur.

The NSCN was a very disciplined rebel outfit until it went into a ceasefire with India BB Nandy, retired intelligence officer

"This is easily the biggest haul of cannabis in the region," said Donald Ingti, customs chief in north-east India.

The NSCN has been negotiating with the Indian government for the past eight years and the rebels are allowed free movement without weapons.

"It appears the cannabis is grown by farmers in the tribal areas of Manipur, Nagaland and Arunachal Pradesh," said journalist, Pradeep Pareek, who closely follows the drug trade in the region.

"Assam is a favourite exit point used by smugglers to carry cannabis to mainland India," he said.

Many rebel groups in north-east India, like the United Liberation Front of Assam (Ulfa) or the Manipur Peoples Liberation Front (MPLF) punish drug traffickers.

But revenue officials say some groups like the NSCN are linked to the trade.

Many rebel groups in north-east India punish drug traffickers

"The NSCN was a very disciplined rebel outfit until it went into a ceasefire with India but its discipline has seriously suffered," says retired Indian intelligence official, BB Nandy.

"Now its leaders are seeking to raise funds through questionable means."

The NSCN is militarily the most powerful separatist group in India's north-east with nearly 6,000 rebels under its command.