Bombs exploded Sunday in Baghdad and the northern oil center of Kirkuk, killing more than 60 people, police said, and dramatically escalating tension as the prime minister left for Washington for talks on reversing the country's slide toward civil war. The blasts occurred as Iraqi forces and the US-led coalition mounted a major crackdown on the country's most feared Shi'ite militia, the Mahdi Army, blamed by Sunnis for many of the sectarian kidnappings and killings which threaten to tear the country apart. The Baghdad bombing occurred when a suicide driver detonated a minivan in the Mahdi Army stronghold of Sadr City at the entrance to the Jameelah market, packed with shoppers and vendors on the first day of the Iraqi work week. An Iraqi army statement said 34 people were killed and 73 were wounded. Eight more people were killed and 20 wounded when a second bomb exploded two hours later at a municipal government building in Sadr City, the Iraqi army said. The wave of bombings, shootings and sectarian killings has plunged Iraq's new unity government into a deep crisis only two months after Prime Minister Nouri al-Maliki took office, pledging to pursue national reconciliation and to pave the way for a US military withdrawal.