A bomb planted inside a minibus went off in a crowded market in the Shi'ite neighbourhood of Sadr City on Sunday, killing five and wounding 35 others, police said. At least seven people were killed in two additional separate attacks in Baghdad also on Sunday. A car bomb exploded in northern Baghdad killing two people and wounding four others and five female pupils were killed in a mortar strike on a secondary school in the predominantly Sunni Adil district of western Baghdad. Meanwhile, a bomb in a Baghdad market kills four, wounds 18. A bomb planted inside a minibus went off in a crowded market in the Shi'ite neighbourhood of Sadr City on Sunday (January 28), killing five and wounding 35 others, police said. An eye witness at scene of attack said that the attack was caused by a suicide bomber who blew himself up among the traders. "What is this? What is this? Islam can not accept this act, to blow oneself up inside a market, beside those men who are here working to earn their living. It is a difficult situation and I'm shaking from seeing the flesh (of the suicide bomber) everywhere," he said. Sadr City is a stronghold of the Mehdi Army, a militia loyal to radical Shi'ite cleric Moqtada al-Sadr, and the area has been hit by a number of major car bombings in recent months. The Mehdi Army has been identified by Washington as the greatest threat to security in Iraq because of accusations it operates death squads responsible for torturing and killing dozens of people whose bodies turn up every day around Baghdad. Meanwhile, a car bomb exploded in northern Baghdad on Sunday killing two people and wounding four others, police sources said. The attack took place in Al-Qahera district near the Sunni-populated neighbourhood of Adhamiya. Television footage showed a car on fire and thick black smoke billowing from it as police vehicles and fire engines were at scene. U.S. military Humvees could also seen converging on the blast scene. In a separate attack, five female pupils were killed in a mortar strike on a secondary school in the predominantly Sunni Adil district of western Baghdad, the school's principal told Reuters. Principal Fawziya Swadi said two mortars landed in the schoolyard where many pupils were gathered. The blasts blew in windows of classrooms, spraying pupils with glass shards that accounted for some injuries. She said 20 people were wounded. Trail of fresh blood could be seen in the yard and corridor of the school and books soaked in it. Wounded pupils were taken to Al-Nu'man Hospital in Adhamiya neighbourhood for treatment Police confirmed the attack, one of many tit-for-tat mortar strikes in Sunni and Shi'ite areas of the capital every day. Also on Sunday, a bomb exploded in a market in western Baghdad killing four and wounding 18, police said. They said that the bomb was left in a cart that was loaded with foodstuff in a crowded market in al-Bayaa district of western Baghdad. The wounded were taken to a nearby local hospital for treatment. Iraq is gripped by tit-for-tat sectarian killings between majority Shi'ites and Sunni Arabs once dominant under Saddam Hussein but now the backbone of the insurgency. Thousands of Iraqis have been killed in violence many Iraqis fear is pitching the country toward all-out civil war.