Abdullah Abdullah, front-runner in Afghanistan's presidential election, escaped assassination on Friday when two bombs blew up outside a hotel where he had just staged a rally, killing six people, Reuters reported.
The midday blasts, one caused by a suicide bomber, destroyed a car in Abdullah's convoy, police spokesman Hashmat Stanekzai said. One of the dead was a bodyguard. Twenty-two people were injured.
Television images showed the charred remains of the car alongside shattered shop fronts in a densely populated western district of Kabul.
"When I was leaving the rally from the People's Islamic Unity Party, our car was hit by a roadside bomb and destroyed," Abdullah said at another rally soon afterwards.
Abdullah, a former leader of the opposition to the Islamist Taliban, came first in the largely peaceful first round of the poll to replace Hamid Karzai, winning 45 percent of the vote.
Former Finance Minister Ashraf Ghani scored 31.6 percent and the run-off between the two leaders is set for June 14.
No one immediately claimed responsibility for the attack on Abdullah but the Taliban, seeking to set up an Islamic state, have vowed to disrupt the election. They could not be reached by phone.
It was the most serious attempt on Abdullah's life since the start of the presidential race and the first such attack close to a rally. In February, he survived an assault on his convoy as he was traveling between the capital and the eastern city of Jalalabad.
By law, the elections must start again from scratch if one of the candidates is killed. Such an event could place the country in an extremely difficult position just months before the pullout at the end of the year of most foreign forces.
The election's first round won praise as an unexpected success after the Taliban, removed from power in 2001 by a U.S.-led invasion, failed to deter millions of voters from turning out in major cities to vote.
The run-off is likely to prove more difficult as the Taliban summer offensive will be in full swing.
The number of weekly attacks rose by around 10 percent to more than 350 incidents - including suicide attacks, gun battles and roadside bombs - in the final week of May, according to a Western security firm.
And recruitment at radical Islamic schools in places like Quetta in Pakistan has intensified as part of the Taliban's campaign to disrupt the vote. [ID:nL3N0OJ1PW]
It was unclear whether the attack near the rally represented a change in tactics following the removal of Taliban commander Mullah Abdul Qayoum from the group's military leadership.
The Taliban denied suggestions that Mullah Qayoum had been dismissed for failing to disrupt the first round and said he had stepped down because of longstanding health issues.