KABUL, Afghanistan -- Hundreds of Afghans protested Saturday against alleged fraud in the country's presidential runoff, part of escalating tensions over what Western officials had hoped would be a smooth transfer of power as violence across the country killed at least 13 people.
Former Foreign Minister Abdullah Abdullah, who is running against Ashraf Ghani Ahmadzai, a former finance minister, has accused electoral officials and others of trying to rig the June 14 vote against him.
Mr. Abdullah announced last week that he was severing ties with the Independent Election Commission and would refuse to recognize any results it releases. He also suggested that the United Nations step in, an idea supported by President Hamid Karzai, who is constitutionally barred from seeking a third term.
The IEC's official timetable says initial results are due on July 2. Independent Election Commission chairman Ahmad Yousuf Nouristani said Saturday that the commission would address or investigate any concern Mr. Abdullah had.
Around a thousand Abdullah supporters gathered in Kabul to protest against the electoral commission, accusing it of fraud and chanting: "Our vote is our blood and we will stand up for it!"
Hundreds of anti-riot police surrounded the demonstration, which was peaceful.
"We gather today to protest against the election commission, which is not an independent commission at all. They are conducting fraud for a specific candidate," said Mohammed Ghani Sharifi, a 23-year-old protester. "The people are so upset and they cannot tolerate such fraud because the people took risks to cast their votes."
While the vote was relatively peaceful, the Taliban had warned people not to participate and carried out a handful of attacks in different parts of the country.
In a separate demonstration, hundreds of Abdullah supporters marched from the northern part of the capital toward the airport, where they were stopped by a police roadblock that preventing anyone from entering or leaving Kabul's international airport.
The U.N. representative to Afghanistan, Nicholas Haysom, told a news conference that people had a "democratic right" to protest while urging them to remain peaceful and "refrain from inflammatory statements."
"We are talking to the candidates even as we speak, and to their teams," Mr. Haysom said. "And at least part of the message that we have for them -- and have had really since the outset -- is that there will be a winner and there will be a loser and what we expect of the candidates is to exhibit statesmanship, not gamesmanship.
He added that the U.N. would also look at ways of bringing "extra scrutiny" to the ballots.
Afghanistan's next president is expected to sign a long-delayed security pact to allow nearly 10,000 American troops to remain in the country after most foreign forces withdraw by the end of the year. Both candidates have promised to sign the pact.
Earlier on Saturday, a suicide car bombing in Kabul aimed at a senior government official killed one civilian but did not harm its apparent target, Afghan security officials said.
Kabul police spokesman Hashmat Stanikzai said the bomber detonated his explosives-laden vehicle alongside the armored car of Mohammed Masoom Stanikzai, a senior official in the High Peace Council, a government body tasked with peace talks with the Taliban insurgency. The two men are not related.
Shafiullah, a police officer at the scene, said Mohammed Stanikzai, who also serves as an adviser to Mr. Karzai, was not harmed because he was traveling in an armored car. Like many Afghans, the police officer only has one name.
At night, gunmen attacked a NATO air base on the outskirts of the eastern city of Jalalabad where the U.S. has forces stationed, Mr. Abdulzai said.
NATO said in an emailed statement that two rockets impacted a base but resulted in no damage to equipment or buildings and no fatalities. The base was later secured, it added.