Authorities were on alert on Friday morning after a sound resembling a blast or a gunshot was heard near a naval base at Porbandar in Gujarat's Saurashtra, but it turned out to be a bursting firecracker, officials said.According to police, the sound was heard by a guard deployed at the naval base, following which a search operation was launched."The sound heard at Porbandar was from a firecracker," Navy spokesperson Captain D.K. Sharma said.Defence bases across the country have been put on alert since the attack on the Indian Air Force base in Pathankot in Punjab in January.An army camp in Uri in Jammu and Kashmir was attacked by terrorists on September 18, in which 19 soldiers were killed. It was followed by surgical strikes by the Indian Army along the Line of Control on the intervening night of September 28-29.On Wednesday, the Border Security Force seized a boat with nine Pakistanis on board in the Sir Creek area adjoining Gujarat's Kutch district close to the Pakistan maritime border.