KABUL, Afghanistan (CNN) -- Security remains a top concern, as Afghanistan holds its second-ever presidential election Thursday, prompting the government to ask for a ban on media coverage of violence.



An Afghan police officer walks near a bank in Kabul where an armed robbery ended in a gunbattle.



Afghanistan's government has ordered the media to refrain from covering possible attacks on election day in an effort to "ensure the wide participation of the Afghan people."



"If anybody broadcasts or gives news about any movements or activities of terrorists, domestic media offices will be closed, and foreigners will be kicked out of the country," according to a statement from Foreign Ministry spokesman Ahmad Zahir Faqiri.



He said the order is in line with Afghanistan's constitution, which allows for such mandates "in exceptional situations" to protect "national interest and national security."



Escalating violence in the capital, Kabul, this week has made some Afghans think twice about whether to venture out to vote.



"If we are not at peace, why should we vote, who should we vote for?" asked Ferishta, 21, who last weekend lay in a blood-soaked shirt and was connected to an intravenous drip after a suicide bombing.



But at least one independent news agency refused to heed a blackout on reports of violence. Restricting media freedoms has no basis in the Afghan constitution, said the Kabul-based Pajhwok News Agency.



The U.S. Embassy in Kabul insisted that press freedoms are necessary to ensure credible elections.



"While we recognize the sovereign rights of the Afghan government and note their intention to encourage Afghans to turn out and vote, we believe that free media reporting is directly linked to the credibility of the elections and continue to support the freedom of the press and responsible reporting," spokeswoman Fleur Cowan said in an e-mail.



On the eve of the election, roadside bombs killed three Afghan election workers in the southern province of Kandahar, and four others were killed Tuesday in the northern province of Badakshan, Independent Election Commission of Afghanistan spokesman Noor Mohammad Noor said.



Amid the violence, the candidates wrapped up last-minute campaigning with the hope that the elections can showcase their country's fledgling democracy.



"We're at a moment of truth," said Mark Schneider, senior vice president of the International Crisis Group, an independent advisory and analysis organization.



An incumbent president and about 40 challengers, including two women, are on the ballot, vying for the votes of what the election commission says are an estimated 17 million registered Afghans against a backdrop of war, graft, poverty and illiteracy.



More than 3,000 donkeys, 3,000 cars and three helicopters will traverse harsh terrain to carry voting materials to remote polling stations, the election commission says. And 30 observer groups, domestic and international, will be on hand to help guard against fraud, it says.



At the heart of every vote will be the two biggest impediments to progress in one of the poorest nations in the world: stifling corruption and an increasingly bloody Taliban insurgency.



International donors are helping pay for the $223 million electoral undertaking, and hundreds of U.S. Marines and Afghan soldiers have moved into strife-torn southern Afghanistan to protect voters against possible Taliban attacks.



The top U.S. envoy to the region, Richard Holbrooke, expressed optimism that Thursday's vote would be Afghanistan's moment to shine. It's tough to organize elections during a war, he said, but the reality is that violence during elections is commonplace in many parts of the world.



"Afghanistan has never had a contested election," Holbrooke said. "So this is a remarkable experiment in democracy and something that Afghanistan needs to give legitimacy to the new government."



That legitimacy has become a key issue in the campaign. Frontrunner President Hamid Karzai's chief challengers -- former Finance Minister Ashraf Ghani and former Foreign Minister Abdullah Abdullah -- have both lashed out at the incumbent for failing to rein in corruption.



In its annual global corruption perception index in 2008, Transparency International ranked Afghanistan 176 out of 180 countries and said graft is "a
Which country was the media blackout in? What number of election workers died in roadside bombs? How many election workers were killed? Who is facing challenges from former ministers? Where is the fresh violence in Afghanistan centred? What are the voters top issues? What killed the election workers? Where is the the media blackout?
Afghanistan three three Afghan President Hamid Karzai's Kabul, Security roadside bombs Afghanistan
question: Which country was the media blackout in?, answer: Afghanistan | question: What number of election workers died in roadside bombs?, answer: three | question: How many election workers were killed?, answer: three Afghan | question: Who is facing challenges from former ministers?, answer: President Hamid Karzai's | question: Where is the fresh violence in Afghanistan centred?, answer: Kabul, | question: What are the voters top issues?, answer: Security | question: What killed the election workers?, answer: roadside bombs | question: Where is the the media blackout?, answer: Afghanistan