A suicide bomber believed linked to the Islamic State in Syria set off a powerful blast Tuesday in one of Istanbul's most popular tourist districts, officials said, killing at least 10 people and injuring 15 with reports citing Germans as among the main casualties.<br />The attack in the shadow of the famous Blue Mosque was a further sign of the country's deepening instability in a region wracked by war and the expanding reach of groups such as the Islamic State, which uses Turkey as a critical lifeline for recruits, supplies and oil smuggling.<br />Turkey's prime minister, Ahmet Davutoglu, described the bomber as a member of the Islamic State, but gave no other immediate details.
