No group has claimed the responsibility for the attack so far.
A six-year-old Afghan girl was reportedly killed in the attack.
Another interior ministry spokesman, Nasrat Rahimi, said it was not clear if there were foreign casualties following the blast.
A police official said a suicide bomber had struck in the Afghan capital, Kabul, after a loud explosion was heard in an area close to foreign embassies on Friday.
Interior ministry spokesman Najib Danish says the bombing took place in the Qabil Bay area of Kabul where many expatriates reside.
Residents walk though the site of a suicide attack in Kabul, Afghanistan.
"Unfortunately, around 9am, a vehicle bombing took place in Qabil Bay area of Kabul". The cause of the explosion was a auto bomb in the city's Qabl Bai area, according to Interior Ministry spokesman Najib Danish. A security source confirmed the embassy's account to AFP.
Ghani made his plans known this week, during a highly successful global peace talks in Kabul, which made USA officials believe and hope that the longest war in USA history may be heading to a settlement.
The Afghan capital has seen a spate of deadly attacks carried out by the Taliban and the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group, whose affiliate in Afghanistan has grown in recent years.
The Conference will look to finding a peaceful solution to decades of war in Afghanistan by bringing the Afghan government, the Taliban and other warring parties into direct peace talks as the initial process.
USA ambassador in Kabul John R. Bass hailed Ghani's "very courageous stand" and his "commitment to pursue a peaceful settlement through talks" after more than 16 years of conflict, as officials said the onus was now on the Taliban to respond. They have not yet offered a full response to the president's proposal, but the apparent openness to negotiations on both sides has sparked cautious optimism. American officials are also braced for more fighting in spring.
The Taliban claimed the ambulance attack, as well as an attack a week prior in which militants stormed a luxury hotel in Kabul, killing 22 people, including 14 foreigners, and setting off a 13-hour battle with security forces.