Turkish police on Thursday detained the suspected driver of the car used in an attack on the US consulate in Istanbul this week, in which 6 people were killed, media reports said. The car had also been seized and the driver was being questioned at police headquarters, CNN Turk reported. Earlier in the day, police detained four other suspects. Interior Minister Besir Atalay described the incident on Wednesday, in which three policemen and three gunmen were killed, as a suicide attack. It came amid rising tensions in Turkey, with the ruling party under threat of being banned for alleged anti-secular activities and police investigating a shadowy far-right group suspected of plotting a military coup. Security was tightened around Istanbul's diplomatic missions and busloads of police were stationed at the site of the attack outside the high-walled consulate. Al-Qaeda link probed Police were investigating whether Al-Qaeda was behind the attack. Newspapers reported that the gunmen who carried it out had received weapons training in Afghanistan. Atalay daily said only one gunman seemed to have traveled abroad. Erkan Kargin, one of the three attackers killed by police outside the consulate, had traveled previously to Afghanistan, according to a government official, who spoke on condition of anonymity because he was not authorized to speak to the media. Dozens of militants from Turkey have had military training in Al-Qaeda camps in Afghanistan and some also fought and died in Al-Qaeda ranks in Iraq, Turkish officials say. If Kargin's suspected relationship with Al-Qaeda is confirmed, the police are likely to label the attackers as militants linked to Al-Qaeda in Turkey, said Emin Demirel, a Turkish terrorism expert. Some security experts were skeptical about an Al-Qaeda link, given the small scale and amateurish nature of the attack. Homegrown militants have been posing an increasing threat to Turkey. As a US ally, it is a high-profile target for militants who subscribe to Al-Qaeda's world view. “It would not be wrong to assume that Al-Qaeda would have instructed cells in Turkey to act,” said Ihsan Bal, head of terrorism studies at International Strategic Research Organization.