ISTANBUL—A powerful car bomb exploded in the center of Ankara on Wednesday, killing at least 28 people and wounding 61 in an attack that targeted a military convoy, according to Turkish officials.

The blast hit Turkey’s capital during a busy evening rush hour, creating a massive fireball that consumed nearby cars and buses. Panicked residents rushed for safety as a dark plume of smoke rose over the city.

The explosion rattled a country that is becoming a more frequent target of such attacks. While there was no immediate claim of responsibility, Turkish officials said their initial suspicions were focused on the outlawed Kurdistan Workers’ Party, or PKK, which has been embroiled in a deadly conflict with the government since a two-year cease-fire broke down last summer.

Recent attacks have also been linked to Islamic State extremists, who were accused of carrying out a suicide bombing in Istanbul last month that killed 10 German tourists.

No matter who is responsible, Wednesday’s blast is likely to empower Turkey’s military hawks pushing for a more aggressive response to the increasing threats destabilizing Turkey, said Sinan Ulgen, a former Turkish diplomat who is now a visiting scholar at the Europe branch of the Carnegie Endowment for International Peace.