Indian and Pakistani border guards exchanged heavy fire Friday evening on the international border in Jammu and Kashmir's Samba district, police said."Pakistan Rangers started unprovoked firing at four BSF (Border Security Force) outposts on the international border in Ramgarh sector of Samba district around 9.30 p.m. after which BSF retaliated effectively at all these places," a senior police official here told IANS."Heavy firing exchanges were going on between the two sides when last reports came in," he added.On Wednesday, a BSF trooper was killed and another injured in Pakistan firing in the same area. Two Pakistan troopers were also killed in retaliatory firing by the BSF.