Istanbul — A car bomb killed 13 soldiers and injured 48 other people on a bus in central Turkey early Saturday, the military said in a statement. Civilians were among the wounded.

All the indications pointed to the banned Kurdistan Workers’ Party as being behind the attack, Deputy Prime Minister Numan Kurtulmus told broadcaster NTV.

But he said it was too early to definitively assign blame.

There was no immediate claim of responsibility for the attack in Turkey, which has been battered by a wave of bombings this year.

Interior Minister Suleyman Soylu said seven suspects had been arrested and five others were being sought.

The governor of Kayseri province, Suleyman Kamci, referred to the incident as a “terrorist attack,” saying a suicide bomber had set off the explosives-laden vehicle.

The off-duty soldiers had been on a shopping excursion in Kayseri province, broadcaster NTV reported.

The explosion took place on a road near the Erciyes University around 8:45 a.m. local time. Kayseri province is about 185 miles south of the capital, Ankara.

The bus was hit on its left side by the explosion and the first images from the scene showed smoke rising from the vehicle and fires still burning in the surrounding area, which was covered in snow.

The pro-Kurdish Peoples’ Democratic Party condemned the blast “in the strongest possible terms. The party has been under increasing pressure from the government, which accuses it of links to terrorism — charges that the pro-Kurdish movement strongly denies.

Last weekend, a car bomb and suicide bomber exploded outside a football stadium in Istanbul, killing 44 people, including 36 police officers. A hard-line Kurdish militant group, the Kurdistan Freedom Falcons, claimed responsibility for that attack.