Sahin said the blast likely was "a terrorist attack," Today's Zaman reported.
Another Turkish government official said earlier no one died in the explosion.
Turkish President Abdullah Gul, in Germany on an official visit, also called the explosion a terrorist attack, Today's Zaman said.
"There are fatalities. I would like to first deliver my condolences to them," Gul said. "I condemn the attack with hatred."
Deputy Prime Minister Bulent Arinc also said preliminary findings point to a bomb attack, noting, "there is information that a bomb was planted" on the vehicle that exploded in front of the Cankaya District Governor's Office and an elementary school, and near a government building.
The New York Times reported Sahin as saying the blast and subsequent fire started in a car with a liquefied petroleum fuel tank.
Security officials blocked the area while bomb squads searched parked cars and buildings where the blast took place. Officials said several cars and buildings were damaged.
Police haven't ruled out the possibility the explosion may have been carried out by the outlawed Kurdistan Workers' Party, the Times reported.
Elsewhere, police said they acted on a tip and found a bomb on the Siirt Kurtalan Express train after it was stopped at Kirikkale train station in Kirikkale province, Today's Zaman reported. Bomb disposal squads defused the device.
Eight passengers were detained in the incident, officials said.