A strong explosion of unknown origin shook the busy shopping street of Istiklal in Istanbul on Sunday, leaving six people dead and wounding dozens more, President Recep Tayyip Erdogan said. Turkey's vice president said a suicide bomber carried out the attack. "It might be wrong if we say for sure that this is terror but according to first signs... there is a smell of terror there," Erdogan told a televised press conference. "The relevant units of our state are working to find the perpetrators... behind this vile attack," he said.