At least 25 Pakistani security officials, including two officers were killed and 15 others injured when Nato helicopters opened fire on Salala check-post in Mohmand tribal region near Afghan border, officials sources said on Saturday.The Inter-Services Public Relations (ISPR) said in a statement that the Nato helicopters opened unprovoked and indiscriminate fire on Pakistani check-post, however it declined to confirmed the death toll . The ISPR said more details were being collected regarding the incident. The attack took place around 2 a.m. in the Baizai area of Mohmand, where Pakistani troops are fighting Taliban militants. The sources said that the dead and injured were shifted to a nearby hospital where condition of several personnel were critical. The two officers who were killed identified as Major Majid and Captain Usman. Nato confirmed the attack and said they were gathering information regarding the incident.