Two alleged robber gang leaders and a drug trader were killed in separate 'gunfights' with police and Rapid Action Battalion (Rab) in Pabna, Dinajpur and Bagerhat on early Tuesday.   In Pabna, Sarwar Saro alias Shahin Alam, 36, son of Harun-or-Rashid, of Santhia upazila, was killed in an alleged gunfight with police.   Goutam Kumar Biswas, additional superintendent of police, said acting on a tip-off, police and Detective Branch members jointly raided Shamukjani Bazar in Santhia upazila at 2am.   As soon as the law enforcers reached the area, the robbers opened fired, triggering a skirmish, the ASP added.   Sarwar, injured in the gunfight, was arrested from the spot and taken to Pabna General Hospital where the doctor pronounced him dead, the police officer said.   In Dinajpur, alleged drug trader Md Ferdous Fahim, 38, of Aolakuri village in Birganj upazila was killed in a reported gunfight with police.                                    Moniruzzaman Monir, officer-in-charge of Birampur Police Station, said tipped-off that drug traders were bringing drugs from bordering area, police took position beside Mirpur field.   The drug traders fired at police and Fahim was killed in the ensuing gunfight, the OC said.   He was accused in several cases, he added.   A pipe gun, three bullets, three cartridges, a sharp weapon, two daggers and 100 bottles of phensedyl were recovered from the spot.   In Bagerhat, an alleged robber gang leader was killed in a reported gunfight with Rab in Kodalia canal area under Sundarbans East Zone under Mongla upazila.   The deceased was identified as Faruk Moral, 38, son of Akbar Moral, a resident of Kolabagi village under Dacope upazila in Khulna.   Lt Col Rawshanul Firoz of Rab-6 said they conducted a drive in the area at 7am in the morning.   As soon as they reached the area, robbers fired at them triggering a skirmish that lasted for about 40 minutes, he added.   Later, Rab arrested Faruk from the spot and took him to Mongla Upazila Health Complex where the doctor declared him dead, he said.   Faruk formed a gang of five to six robbers a few days back and committed robbery in the area, the Rab official said quoting local fishermen.