At least 55 people were killed and scores wounded Monday on a day of deadly violence in Iraq that saw government and security buildings stormed in two cities. According to dpa, a car bomb went off in front of the local police headquarters in Baiji, 210 kilometres north of Baghdad, after which attackers forced their way into the building, killing four policemen, security officials said. The building was later retaken by security forces, and six attackers slain. There was a similar attack on the provincial council building in nearby Tikrit in which four people, including a member of the council, were killed, before the building was recaptured by commandos. In Tel Afar, near the northern city of Mosul, gunmen opened fire on a bus, killing 12 and injuring seven, Alsumaria television reported. In the capital Baghdad, three separate car bomb attacks in the city centre killed 10 people and injured more than 20. A blast in south-western Bayaa district killed two people and wounded 10, Alsumaria said. A series of attacks in Diyala province, north of the capital, killed nine people and injured 13. The dead included four soldiers in an army training camp that was targeted by a suicide bomber in an explosives-laden car. Security forces in the province also arrested 10 people suspected of killing 18 mostly Iranian gas pipeline workers last Friday. Attacks on security forces in Nineveh, Kirkuk, Salah al-Din and al-Anbar provinces killed eight people and injured 13.