At least 25 security personnel including 2 officers, have been martyred and several others injured in unprovoked firing by NATO helicopters on 3 Pakistani check posts in Mohmand Agency, source said on Saturday. Pakistan has suspended NATO supplies and lodged strong protest with the U.S. and NATO. Pakistan has also issued a strong worded memo to the U.S. State Department on this count while NATO has said the matter is being investigated. NATO planes shelled 3 check posts including Salala, and Bolder located in Tehsil Balazai of Mohmand Agency late Friday night. Sources said that 25 security personnel including one Major were killed and 15 were injured. The incident sparked harassment in the area while bodies of martyrs and injured personnel have been shifted to hospital. The army spokesman confirmed the incident and said details about the unprovoked shelling are being collected. The ISPR spokesman said NATO helicopters resorted to unprovoked firing. On the other side NATO spokesman said in Kabul that he is aware of the incident and the matter was being investigated. Pakistan embassy in Washington has issued strongly worded memo to the U.S. State Department on this incident. Pakistani Counsellor Riffat Gardezi informed the U.S. authorities about this incident and recorded Pakistan strong protest against unprovoked firing by NATO helicopters. The wounded soldiers were airlifted to Peshawar. Separately, seven militants were killed in a clash with security forces in Masozai area of Kurram Agency. Four security personnel were also injured. So far more than 100 militants were killed by security forces during the last two weeks in different parts of Kurram tribal belt. Besides, dozens of militant hideouts were also destroyed. Ten troops, including a major, also embraced martyrdom.