The leading Afghan presidential candidate, Abdullah Abdullah, narrowly escaped an assassination attempt Friday when two bombs struck his convoy after a campaign event in the capital, a reminder of Afghanistan's fragility as it prepares for its first democratic transfer of power with foreign combat troops set to withdraw by the end of the year.

The attack killed six civilians but Abdullah was unharmed and went on to speak at a campaign rally. Although there was no immediate claim of responsibility, it bore the hallmarks of Islamic militants fighting against the Western-backed government.

"My car was the target," Abdullah told Tolo TV after the attack. "It was a big conspiracy against me."

At the rally, Abdullah told the crowd that his "vehicle was destroyed, but fortunately we escaped it unharmed. Unfortunately a number of our security guards were wounded in the incident, but thankfully their injuries are not so serious."

The attack came just over a week before a runoff vote in which Afghans are to choose a new leader to replace outgoing President Hamid Karzai. The Taliban have vowed to disrupt the balloting, though the first round on April 5 was relatively peaceful. The attempt on Abdullah's life appeared to be the first direct attack on one of the candidates, as earlier attacks targeted only campaign offices and workers.

Karzai condemned the attack, saying it was staged by "enemies of Afghanistan who don't want free elections."

Interior Ministry spokesman Sediq Sediqqi said there was a suicide bombing followed by a roadside bomb. He said nobody in Abdullah's entourage was killed. The ministry later issued a statement saying six civilians were killed and 22 were wounded.

But Kabul police chief Mohammed Zahir said both explosions were carried out by suicide bombers -- the first was a driver who blew up a vehicle and the second was a suicide bomber on foot. Conflicting accounts are common in the chaotic immediate aftermath of attacks in Afghanistan.

The blasts destroyed several cars and nearby storefronts, leaving the street littered with twisted metal and other rubble.

Abdullah, a former Afghan foreign minister, was the runner-up in the disputed presidential elections of 2009 and is now a leading candidate to succeed Karzai, who is constitutionally barred from seeking a third team.

Abdullah is running against former Finance Minister Ashraf Ghani Ahmadzai in the second round scheduled for June 14. In the initial balloting, Abdullah garnered 45 percent of votes while Ahmadzai came in second with 31.6 percent. Former presidential candidate Zalmay Rassoul, who is now supporting Abdullah, also was in the convoy Friday but was not injured.

The vote comes at a pivotal time as the international community prepares to withdraw combat forces by the end of the year. Both Abdullah and Ahmadzai have pledged to sign a security pact with the U.S. that will allow thousands of foreign forces to remain in the country after 2014 in a training and advisory capacity. The new president will face the daunting task of resetting relations with Washington, which have taken a battering from Karzai's increasing anti-American rhetoric.

During the Soviet occupation in the 1980s, Abdullah served as adviser to and spokesman for Tajik warlord Ahmad Shah Massoud, who was assassinated by Al Qaeda two days before the Sept. 11, 2001 attack.

In the early days after the U.S.-led alliance toppled the Taliban, Abdullah became the face of Afghanistan's anti-Taliban movement, giving frequent press conferences to international media.