Reports from Afghanistan say an explosion and gunfire were heard at the Kabul residence of presidential candidate Ashraf Ghani.
Ghani reportedly was not at home at the time and has since communicated via social media.
AP quotes police official Sayed Gul Aga Hashmi as saying the attack was carried out by two suicide bombers.
He said one attacker detonated his car and the other set off his explosives vest. He said police are hunting for a third suspect.
There were no immediate reports of casualties.
A Reuters cameraman had said he could hear continuous gunfire.
Ghani is a former World Bank official and Afghan finance minister who has picked powerful former Uzbek warlord Abdul Rashid Dostum as his running mate.
In a tweet sent after the incident, Ghani said he had just arrived in Gardez, south of Kabul, for a campaign rally.
The Taliban has vowed to use violence to disrupt Afghanistan's April 5 presidential election.
Based on reporting by Reuters and AFP