BAGHDAD - Multiple car bombings in predominantly Shi'ite districts of Baghdad killed at least 30 people on Saturday, police and medics said, the latest in a series of attacks that threaten to sink Iraq once again into full-blown sectarian conflict.Most of the attacks struck in busy commercial areas where people had gathered to shop and socialize after breaking their daily fast for the Muslim holy month of Ramadan.The deadliest explosion took place in the northern neighborhood of Tobchi, where 10 people were killed when a car bomb exploded in a busy commercial street."I was standing near my shop with friends when we saw a parked car that aroused our suspicions. We shouted for the driver, but no-one answered" said shopkeeper Said Mohammed Murad."Minutes later, the car blew up, smashing shopfronts and throwing passers-by like toys. All that was in front of me was fire, smoke, dead bodies, and wounded people crying for help."Another car bomb exploded in a commercial street in the Karrada neighbourhood, killing at least four people. There were further blasts in Zaafaraniya, Muwasalat, al-Shurta and New Baghdad.It was unclear who was behind the blasts. Sectarian tensions in Iraq have been inflamed by the civil war in neighboring Syria, which has drawn in Shi'ite and Sunni fighters from Iraq and beyond to fight on opposite sides of the conflict.Sunni insurgents, including the al-Qaida-affiliated Islamic State of Iraq, have been recruiting from Iraq's Sunni minority, which resents Shi'ite domination since the US-led invasion that toppled Saddam Hussein in 2003. "The terrorists are now using different tactics that aim to cause higher casualties among civilians," said an interior ministry official on condition of anonymity.More than 535 people have been killed in militant attacks in July so far, according to violence monitoring group Iraq Body Count.That is still well below the peak of sectarian bloodletting in 2006-07, when the number of people killed in militant attacks sometimes exceeded 3,000 in one month.In the town of Madaen, about 30 km (20 miles) southeast of Baghdad, a bomb planted in the garden of a Sunni government-backed "Sahwa" militia fighter killed five people, police said."Sahwa" members are often targeted by Sunni insurgents in revenge for cooperating with the Shi'ite-led government.