Kabul - Militants on Tuesday launched a suicide attack near an Afghan election commission office, police said, close to the Kabul home of a leading candidate for the presidential poll.
The Taliban have vowed a campaign of violence to disrupt the ballot on April 5, urging their fighters to attack polling staff, voters and security forces in the run-up to election day.
Blasts were heard mid-morning in the western Darulaman area of the Afghan capital near the house of Ashraf Ghani, who is seen as a frontrunner in the race to succeed President Hamid Karzai.
"It was a suicide bomb attack near an IEC [Independent Election Commission] branch office," Kabul police spokesman Hashmat Estanakzai said.
A member of Ghani's campaign team said the former World Bank economist was out of Kabul at the time, campaigning in the eastern province of Paktia.
"The attack is not at doctor Ashraf Ghani's house, it is at another building nearby," the source said.
Witness Ahmad Sharif, a government employee, said he heard two loud explosions followed by gunfire.
IEC spokesman Noor Mohammad Noor said security forces had told them their office may be the target of the attack.
"We have spoken to our staff in that office, they are all fine and are in their bunkers," Noor said.
There was no immediate claim of responsibility but suicide bombings have been a key weapon for Taliban militants in their fight against Karzai's government and its foreign backers since 2001.
Leading election candidates
On Thursday four gunmen stormed Kabul's Serena hotel and shot dead nine civilians including an Agence France-Presse journalist, an attack claimed by the Taliban.
The Serena attack came on the same day that seven Taliban suicide attackers invaded a police station in the eastern city of Jalalabad, killing 10 policemen.
And last Tuesday, a suicide bomber killed 16 people at a crowded market in the northern province of Faryab. There was no claim of responsibility for that attack.
Previous Afghan elections have been badly marred by violence as the Islamist militants displayed their opposition to the US-backed polls.
Another bloodstained election would damage claims by international donors that the expensive intervention in Afghanistan has made progress in establishing a functioning state.
US-led Nato combat troops are withdrawing from the country after 13 years of fighting a fierce Islamist insurgency, which erupted when the Taliban were ousted from power after the 9/11 attacks on the United States.
Relations between Karzai and the US have been severely strained over the president's decision not to sign an agreed deal for a small US force to remain in Afghanistan from 2015 on counter-terrorism and training operations.
Apart from Ghani, the other leading election candidates are Abdullah Abdullah, who came second in 2009, and former foreign minister Zalmai Rassoul.