ISTANBUL—A bomb blast wounded eight people at a bus stop close to a police school in Istanbul Thursday morning. It wasn't yet known who was responsible or why the bomb was planted.

Istanbul Police Chief Huseyin Capkin said the blast was caused by a medium-power explosive attached to an electric bicycle, which detonated at 8:58 a.m. local time. Eight people, including a passing police officer, were injured in the explosion, but none had suffered life threatening injuries, officials said.

The...