BAQUBA (AFP) - A string of suicide attacks against Iraqi security forces killed at least 37 people on Tuesday, including 28 when two suicide bombers blew themselves up among a crowd of recruits at an army base. The two bombers, one of whom wore an Iraqi military uniform, detonated their explosives-filled vests at a recruitment centre on the Al-Saad base, east of the Diyala provincial capital of Baquba, a security official said. At least 55 people were also wounded in the morning attack, which came ahead of a promised Iraqi army offensive in the province, an Al-Qaeda stronghold just north of Baghdad. "We were about 30 people standing at the entrance," said one of the wounded, Falah Ali Hussein, 17. "They had just called our names when suddenly there was a big explosion." A police officer said the victims were from a first batch of men called from across the province to participate in a military recruitment drive. "The bombers blew themselves up amid the crowd. One bomber was dressed in Iraqi military uniform, while the other was wearing civilian clothes," the officer said. The US military said 20 Iraqi army recruits were killed and 55 wounded. The base has a joint Iraq-US security post but the American military said it suffered no casualties. Victims were ferried in ambulances and police vans to the nearby hospital in Baquba where relatives rushed to find their loved ones. Pictures taken by an AFP photographer at the hospital showed the wounded being treated in the lobby which was quickly covered with blood as dozens of victims were brought in. Outside, a police officer was seen crying next to the body of his slain younger brother, while television footage showed several women searching among the bodies to identify their sons who had gone to the military base. Diyala and its capital Baquba remain one of the most dangerous areas in Iraq with frequent suicide attacks, including several by female assailants, as well as car bombings. Suicide bombers also struck in Iraq's main northern city of Mosul, another Al-Qaeda stronghold. Police Major Shahab Ahmed said five people were killed and six wounded when a suicide bomber blew up his vehicle near a police patrol in the Al-Noor neighbourhood in the east of the city. Four people were killed and five wounded when a second bomber blew himself up close to a police patrol in the Ras al-Jad'a district of the city centre, he added. Doctor Ahmed Jassim from Mosul hospital confirmed that nine bodies had been brought in from the two attacks. A car bomb also exploded in Mosul wounding six people, Ahmed said. In the capital, Electricity Minister Karim Wahid escaped unharmed when a roadside bomb exploded in east Baghdad, wounding three of his bodyguards, security officials said. Tuesday's bloodshed came as US commanders hailed a fall in overall violence in Iraq to a four-year low.