Kolkata: In a sinister twist to the menace of cattle smuggling along the India-Bangladesh border, the BSF on Thursday recovered cows with improvised explosive devices (IED) tied around their necks aimed at targeting troops who try to catch them.

Border Security Force officials said this is the first time they have come across this cruel method that can potentially lead to fatal injuries to both the cattle and force personnel, in case the crude bomb is triggered during handling.

Few such cattle, with an IED placed inside a small aluminium canister tied around their neck, were recovered from the river near the Harudanga border post along the south Bengal frontier, they said.

After being tied with banana trunks and ropes, the cattle were dropped in monsoon-water laden rivers from Malda, Murshidabad, North 24 Parganas and Nadia districts, officials said.

"We are studying the type of IED prepared by the smugglers that is aimed to scare BSF troops from intercepting cattle smuggling incidents. A total of 365 cattle being smuggled across the border to Bangladesh have been recovered since Wednesday," they said.

In an another incident, a group of narcotics smugglers attacked and lobbed a country-made bomb towards a Border Security Force patrol in the early hours of Thursday in the Berhampore sector.

While the troops escaped unscathed, a pump action gun being carried by a jawan was completely damaged by the impact of the blast, they said.

A sudden rise in "floating cattle" instances in West Bengal has prompted the BSF to deploy additional troops, motorboats and surveillance gadgets to curb the crime. Over 1,500 cows and buffaloes have been seized in over two weeks' time at this border area by the force, they said.

The desperation of the smugglers to commit the crime has increased even as the cost per cattle head has gone upto Rs 1.4 lakh, from the earlier Rs 80,000, in anticipation of the Bakrid festivities in August.​