The incident was reported at about 6:30 pm when a Border Security Force (BSF) patrol team detected some suspicious movement along the border post 'Rosse'.
The intruders were challenged and they fired back, the sources said.
After a brief exchange of fire, the intruders hastily fled back, they said.
"The troops involved in the operationreported that there were three intruders with some head-load and a plastic pipe. As the BSF party retaliated, one of the intruders got injured but his accomplices took him back across the international border.
It is one of the biggest seizures of contraband along this border and the cache is estimated to be worth Rs 5 crore in the international market, he added.