An explosion ripped through the centre of Turkey’s largest city on Sunday, killing at least six people and injuring dozens in a possible bomb attack on one of Istanbul’s most high-profie tourist attractions.

Witnesses described a powerful blast followed by panic on Istanbul’s pedestrian-only Istiklal Street, a mile-long stretch of shops, cultural attractions and diplomatic outposts, including the consulates of France and Russia.

“When I heard the explosion, I was petrified, people froze, looking at each other. Then people started running away. What else can you do,”said 45-year-old Mehmet Akus, who works in a restaurant on Istiklal. “My relatives called me. They know I work on Istiklal.”

Turkey’s President Recep Tatyyip Erdogan, speaking to reporters in Ankara before boarding the plane to head to Indonesia for the summit of the G20, described the explosion as a likely terrorist attack.

“It might be wrong to say for sure that this is terrorism, but there is the scent of terror here,” he said. “The relevant units of our state continue their efforts to uncover the perpetrators of this heinous attack and those who orchestrated it.”

Panic erupted as the explosion sent fire and debris flying. “At first we thought a building had collapsed,” said a resident who lives 200 yards from the blast site. “Then we saw the people running down our street.”

Many feared a secondary attack, and reports swirled about gunfire. Panic erupted in another neighbourhood, Nisantasi, amid unfounded claims of another bomb blast. Helicopters swirled above, as succession of emergency vehicles screeched through the city.

Inferno following the blast

Security camera footage showed dozens of people walking by a planter along the street on what had been a sunny Sunday afternoon just before the explosion, which the video suggests could have come from a bag placed on a wooden bench. Grisly video and photos of the aftermath showed bloodied men and women and the body parts of victims scattered across the street.

“We wish God’s mercy on those who lost their lives and a speedy recovery to the injured,” Istanbul mayor Ekrem Imamoglu said in a post on Twitter.

Mr Erdogan said initial investigations suggested a woman had a role in the blast. “Efforts to suffocate Turkey and the Turkish nation with terrorism have not reached results in the past and will not in the future,” he said.

Turkey’s broadcast media watchdog issued a ban on sharing footage of the explosion. Officials cautioned journalists and citizens not to share unverified information about the blast.