north of Baghdad killed 15 people. Later same day, a Sunni mosque in the Dura section of Baghdad was blown up; there were no reports of casualties. January 23 – Five US civilians working for Blackwater USA are killed in Baghdad when their helicopter came under fire and crashed. The helicopter was coming to the aid of a US Embassy convoy that had come under fire, a US diplomatic official said. NBC News reports that four of the contractors were shot execution style. Two Sunni insurgent groups claimed responsibility for the attack. January 25 – Two mortars slam into the Green Zone and a suicide car bomb detonates in a Shiite neighborhood in Baghdad, killing at least 26 and injuring 54. A second explosion in Baghdad occurred later. The attacks came hours after a pledge from Iraqi Prime Minister Nouri al-Maliki that the upcoming security crackdown in Baghdad will track down militants and make the city safer. January 28 – Battle of Najaf (2007), more than 280 people are reported killed. First of the 2007 chlorine bombings in Iraq happens in Ramadi killing 16 people. February February 2 – National Intelligence Estimate on Iraq released by U.S. intelligence. February 3 – A large truck bomb exploded in a busy market in the Iraqi capital of Baghdad. The suicide attack killed at least 135 people and injured a further 339 others. The bomb brought down at least 10 buildings and coffee shops and obliterated market stalls in a largely Shiite enclave less than a half a mile from the Tigris River. February 5 – A car bomb in Baghdad at a petrol station killed 15 people and wounded 65 in the Saidiya district. February 6 – A US Marine CH-46E helicopter from HMM-364 was shot down with a MANPAD over Karmah, Iraq, killing 7, including one Marine from HMM-262. It was the fifth US helicopter to crash in two weeks. A car bomb at a market in Fallujah killed 10 people, including two children, and injured 30 others. February 7 – The much-awaited security crackdown was implemented in Baghdad. A car bomb killed 20 and injured 45 others at a market in Aziziya. February 12 – Three car bombs explode in Baghdad, killing about 76 and wounding some 150 people. The bombings coincided with the first anniversary, according to the Muslim lunar calendar, of the destruction of the Shiite Golden Dome