Officials said the incident occurred around 1 am when troops of the 163rd battalion of the Border Security Force were out on patrol on a Tata-407 vehicle near the Bhikiwind post, which is about 16 kms from the retreat ceremony area in Attari.
"Three troops received bullet injuries. We suspect the shots were fired by smugglers from across the border fencing between the two countries. Further inquiries are on," officials said.
They said a total of 11 rounds were fired after which the alleged shooters ran away.
The BSF has found many empty fired shells from the fencing area, indicating the firing was done from across the border. They said, adding the regular evening retreat ceremony is expected to be held on Saturday.
BSF officers said there have been earlier instances of exchange of fire between smugglers and its troops in this area but this is probably the first time the fire has come from the other side first.
"The BSF patrol fired in retaliation but the suspected smugglers fled taking advantage of the darkness," they said. The BSF has stepped up vigil in the area and senior officers of the BSF's Punjab frontier have reached the area where the incident took place, they said.