BAGHDAD — A wave of bombings tore through Baghdad Tuesday morning, killing at least 56 people in a spasm of violence on the eve of the 10th anniversary of the US-led invasion. The attacks show how dangerous and unstable Iraq remains a decade after the war — a country where sectarian violence can explode at any time. And though attacks have ebbed since the peak of the insurgency in 2006 and 2007, tensions simmer and militants remain a potent threat to Iraq's security forces. Tuesday's attacks were mostly by car bombs and targeted mainly Shiite areas, small restaurants, day laborers and bus stops in the Iraqi capital and nearby towns over a span of more than two hours. Along with 56 killed, over 200 people were wounded in the attacks, officials said. The bombings came 10 years to the day that Washington announced the start of the invasion on March 19, 2003 — though by that time it was already the following morning in Iraq. Also on Tuesday, Iraq's Cabinet decided to postpone upcoming provincial elections in two provinces dominated by the country's minority Sunnis for up to six months. The decision followed requests from the political blocs in the provinces, according to Ali Al-Moussawi, the prime minister's spokesman. The two provinces affected, Anbar and Ninevah, have been at the center of the nearly three-month-long protests against Iraq's Shiite-led government. Provincial elections were scheduled for April 20. One of the deadliest of Tuesday's attacks struck close to one of the main gates to the heavily-fortified Green Zone, which houses major government offices and the embassies of several countries, including the United States and Britain. That blast outside a restaurant killed six people, including two soldiers, and wounded more than 15. A bomb exploded outside a popular restaurant in Baghdad's Mashtal neighborhood, killing four people and wounding 15. It blew out the eatery's windows and left several cars mangled in the blood-streaked street. Minutes later, two day laborers were killed and eight were wounded when a roadside bomb hit the place where they gather every day in an area of New Baghdad. In the poor Shiite neighborhood of Sadr City, a bomb stuck to the underside of a minibus killed three commuters and wounded seven people. Another car bomb exploded in a commercial street in the same area, killing two people and wounding 11, and yet another bomb struck a police patrol in the neighborhood, killing five people and wounding 13. Hussein Abdul-Khaliq, a government employee who lives in Sadr city, said he heard the explosion and went out to find the minibus on fire. “We helped take some trapped women and children from outside the burning bus before the arrival of the rescue teams. Our clothes were covered with blood as we tried to rescue the trapped people or to move out the bodies,” he said. “Today's attacks are new proof that the politicians and security officials are a huge failure,” he said. Other attacks struck the largely Shiite neighborhoods of Hussainiyah, Zafarniyah, Shula and Utaifiya, as well as the Sunni district of Tarmiyah. Just outside the capital, a mortar shell landed near a clinic in the town of Taji, killing two people and wounding five. And about km south of Baghdad, in Iskandiriyah, a car bomb exploded near a bus stop, killing five people and wounding 20.