The attack came just over a week before a runoff vote is to be held as Afghans choose a new leader to replace President Hamid Karzai. The Taliban have vowed to disrupt the balloting, although the first round on April 5 was relatively peaceful. Friday's attack was the first to directly target one of the candidates in Kabul.
Interior Ministry spokesman Sediq Sediqqi said the violence started with 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.
In a televised statement shortly after the attack, Abdullah, who was Karzai's main rival in disputed elections in 2009, said he had not been harmed but some of his security guards had been wounded. Former presidential candidate Zalmay Rassoul, who quit and threw his support to Abdullah, also was in the convoy and was not injured.
Karzai condemned the attack, saying it was staged by "enemies of Afghanistan who don't want free elections."
The blasts destroyed several cars and nearby storefronts, leaving the street littered with twisted metal and other rubble.
Nobody immediately claimed responsibility for the attack, but it bore the hallmarks of Islamic militants who are fighting against the Western-backed government.
The Taliban have unleashed a wave of deadly attacks since the campaign to replace Karzai, who is constitutionally barred from seeking a third term, but the candidates have faced
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.
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-Qaida 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. He served as foreign minister and then was the runner-up in President Hamid Karzai's disputed re-election in 2009.
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 that in a training and advisory capacity.
The new president also will face the daunting task of resetting relations with Washington, which have taken a battering from Karzai's increasing anti-American rhetoric.