A car bomb attack that killed five people in a predominantly Kurdish city this week bears the hallmark of separatist Kurdish rebels, Turkey's prime minister said Saturday during a visit to the area. A bomb-laden car exploded Thursday in front of building packed with students preparing for university entrance, as a military bus carrying soldiers passed by. Four of the people killed were students. The explosion also left 68 people injured, including more than 30 soldiers. "Considering the type of action, it fits the style of the separatist terror organization," Prime Minister Recep Tayyip Erdogan told reporters in Diyarbakir. "That is what our findings show." Police are questioning four people over suspected links to the attack, which authorities have blamed on the rebel Kurdistan Workers' Party, or PKK. No one has claimed responsibility.