Militants blew up 13 cars in three hours, wounding at least 20 people, while 13 Iraqis were killed in other violence that fed the turmoil following last month's contested parliamentary elections. The day's worst bloodshed came in eastern Baghdad, where police said gunmen killed five people at a butcher shop and a bomb killed two police officers at a gas station. Eight of the car bombs exploded in Baghdad and wounded a total of 11 people, police said. Officers later destroyed a ninth car bomb that failed to go off. A suicide car bomber near Tikrit injured six civilians, and in the northern city of Kirkuk, a bomb aimed at an Iraqi police convoy wounded three civilians, police said. Car bombings in the northern city of Kirkuk and in Muqdadiyah caused no injuries. Sunni Arabs made their opening bid Sunday in what could be protracted negotiations to form a new government. Leaders of the minority's main political group, the Iraqi Accordance Front, traveled to the northern city of Irbil for a Monday meeting with the president of the Kurdish region. The Sunni Arab visit to the Kurdish region was the first since the election, whose results have been protested by Sunni and secular Shiite parties. Their trip came as Prime Minister Ibrahim al-Jaafari, a leading member of the governing United Iraqi Alliance, met on Sunday with Kurdish regional president Mazoud Barzani and discussed the outlines of a future coalition government. "We agreed on essential principles for exerting efforts to form a broad-based government, a strong national unity government. Meetings will be continued later here and in Baghdad and we will continue to cooperate until we achieve what is beneficial for Iraq," Barzani said. Two more Iraqis were slain and five wounded by gunfire at a Sunni mosque in southern Baghdad, while a Shiite sheik was fatally shot at a market in the same part of the city. In the northern city of Mosul, about a dozen gunmen attacked a police checkpoint, killing a bystander and wounding three policemen, police said. A gasoline shortage because of insurgents' threats against tanker-truck drivers has added to the unease. Police killed two protesters in the oil-rich northern city of Kirkuk on Sunday when a demonstration by 500 people over rising fuel prices escalated into a riot. Authorities imposed a curfew on the city. The Kurdish region in Iraq's north already has seen a flurry of postelection bargaining between Kurds and the governing Shiite Muslim religious party, the United Iraqi Alliance. Preliminary results from the Dec. 15 election have given the Shiite group a strong lead in the voting for Iraq's 275-member parliament, but not enough for it to govern without other political blocs. A year ago, it took nearly three months of negotiations between the Shiite religious alliance and a coalition of Kurdish parties to form an interim government after a Jan. 30 election that was boycotted by the Sunni Arabs at the core of the insurgency. The first quarter of 2006 looks more crucial as Iraq tries to shape an administration that will govern for four years. U.S. officials are pushing the parties to form a broad-based coalition government, and failed negotiations could worsen the civil strife. "This is perceived, inappropriately or inaccurately perhaps, by the enemy as a time of vulnerability, as the government transitionsâ€¦to the constitutional-based, democratically elected four-year permanent government," said Brig. Gen. Donald Alston, spokesman for the U.S.-led coalition force. Final election results are expected as early as this week, and the Shiite religious bloc may win about 130 seats - short of the 184 seats needed to avoid a coalition with other parties to elect a president. That vote is a prerequisite before a government can be formed. The Kurds could get about 55 seats, the main Sunni Arab groups about 50 and the secular Shiite bloc headed by former Prime Minister Ayad Allawi about 25. A representative of Allawi's group said it had not been invited to the Irbil talks. The Irbil meetings came ahead of Monday's visit to Iraq by a team of international monitors who will assess the elections, which have been endorsed as credible by the United Nations but denounced as rigged by opposition groups. About 1,500 complaints have been registered. "We are highly confident that the international team will look deeply into the complaints regarding the election results, will present its recommendations, and compensate us for the votes we lost," Tarek al-Hashimi, head of the Iraqi Islamic Party, told the Al-Jazeera satellite television channel.