A truck bomb exploded as worshippers left a Shiite mosque in northern Iraq on Saturday, killing at least 63 people and wounding nearly 200 in the deadliest bombing in nearly two months. The blast near Kirkuk - a city rife with ethnic tensions - came hours after the prime minister insisted US troops will leave Iraqi cities by the end of this month "no matter what happens," but acknowledged more violence was likely. The Americans already have begun withdrawing combat troops from inner-city outposts in Baghdad, Mosul and other urban areas ahead of the June 30 deadline. But continued assassinations and high-profile explosions have heightened concerns that Iraqi forces are not ready to take over their own security. Worshippers were leaving the mosque in Taza, 10 miles (20 kilometers) south of Kirkuk, following noon prayers when the truck exploded, demolishing the mosque and several mud-brick houses across the street, according to police and witnesses. Rescue teams searched for hours to find people buried under the rubble while women begged police to let them near the site so they could search for loved ones. The US military said it was providing generator lights and water at the site. Ambulances rushed victims to the overwhelmed hospital in Kirkuk and some victims had to be taken to hospitals in nearby cities. Three babies cried as they were placed on a single hospital bed to be treated. Brig. Gen. Sarhat Qadir of the Kirkuk police force said late Saturday that the discovery of bodies beneath the debris had pushed the death toll to 63, while 170 were wounded. Witnesses said the truck was parked across the street from the mosque and they assumed the driver was praying, although Kirkuk's police chief, Maj. Gen. Jamal Tahir, said investigators were looking into the possibility it was a suicide bombing. "The truck was parked near our house; therefore most of the victims were found beneath the debris of the houses, mostly women and children," said Ehsan Mushir Shukur, whose sister was seriously wounded and taken to the Kurdish city of Sulaimaniyah. He said his wife was also wounded while his sister's young son and daughter were killed. Yellman Zain-Abideen, who was wounded by shrapnel in his hand and face, cried for his missing son who had been leaving the mosque with him when the blast occurred. The 43-year-old father of four blamed local authorities for not providing sufficient security in the mainly Turkomen area, which is surrounded by Sunni villages. "There should have been guards around the mosque, we are living in an area surrounded by enemies," he said. AP Television News footage later showed men using pickaxes and shovels to dig dozens of graves in the cemetery behind the mosque to bury the victims. Nobody claimed responsibility for the attack, but it bore the hallmark of al-Qaida in Iraq or other Sunni insurgents who remain active in northern Iraq despite security gains. Tensions have risen in the oil-rich area as Kurds seek to incorporate Kirkuk into their semiautonomous region despite opposition from Arabs, Turkomen and other rival ethnic groups. Officials also have warned that insurgents are likely to stage more attacks after the withdrawal deadline to try to undermine confidence in the government's ability to protect its people. Saturday's explosion near Kirkuk was the deadliest since April 24 when back-to-back suicide bombings by female attackers killed 71 people outside a Shiite shrine in Baghdad. A suicide car bomber also struck an Iraqi police patrol Saturday in Karmah, a former insurgent stronghold west of Baghdad, killing the three officers, police said. Prime Minister Nouri al-Maliki urged Iraqis to maintain support for government forces, calling the first phase of the US withdrawal plans a "great victory." "Don't worry if some security breach occurs here or there," he said in an address earlier Saturday to members of the ethnic Turkomen community in Baghdad. "They are trying to destabilize the situation, but we will confront them." The US-Iraqi security pact requires the Americans to pull back combat troops from cities by the end of this month as a first step toward a full withdrawal by 2012. The deal includes a provision for the Iraqi government to ask for US help if violence surges. US troops, meanwhile, continued preparing for the withdrawal. On Saturday, American commanders turned over control of a key base on the edge of Baghdad's main Shiite district of Sadr City. The sprawling slum was a militia stronghold that saw fierce clashes until a cease-fire following a US-backed government crackdown. The Iraqis also reopened Zaytoun Street, which had been part of Baghdad's Green Zone, which houses the U.S. Embassy and the Iraqi government headquarters. The Iraqis have begun removing some of the protective blast walls around the Green Zone - part of a campaign to restore a sense of normalcy as violence has waned.