The blast happened at about 16:20 local time (13:20 GMT) on a shopping street in the Taksim Square area, the Turkish city's governor Ali Yerlikaya said.

It is unclear what caused the explosion, which appears to have been captured on social media videos.

President Recep Tayyip Erdogan said the perpetrators would be punished.

There was a heavy police presence around Istiklal Street, which had been cordoned off. Helicopters were circling overhead as ambulances went back and forth.

Eyewitness Cemal Denizci was about 50m (54 yards) away when he heard the explosion. "I saw three or four people on the ground," he told AFP.

"People were running in panic... There was black smoke. The noise was so strong, almost deafening," he said.

The street — usually packed with shoppers — was previously targeted by a suicide bomber in 2016.

Earlier reports had said that number of people have been injured following an explosion on a busy area in central Istanbul.

Turkish authorities have yet to confirm the cause of the explosion or the number of injured, as emergency services were seen rushing to the Taksim area of the city.

Yerlikaya described there being both "casualties and injuries" in a Twitter post, without offering further details.