According to official figures, at least six people were killed and 81 others injured in an attack in the center of the Turkish metropolis of Istanbul.

In the evening, Turkish Vice President Fuat Oktay spoke of a "terrorist attack" on the busy Istiklal shopping street.

This is assumed at the moment, he told journalists on Sunday evening.

A suspect detonated a bomb, he said.

Video footage showed a suspect sitting on a bench for about 40 minutes and getting up minutes before the blast, Justice Minister Bekir Bozdag said.

The identity of the woman has not yet been clarified.

39 of the 81 injured have now been discharged from the hospital, Turkish Health Minister Fahrettin Koca tweeted.

Of the 42 people who were still being treated, five were in intensive care, two of them were considered seriously injured.

Shortly after the incident, Turkish President Recep Tayyip Erdogan spoke of a "vile attack";

those responsible would be “unmasked”.

Attempts of "terrorism" against the Turkish people are doomed to fail.

It might be wrong to speak definitively of terrorism, the President said.

But the metropolitan governor, Ali Yerlikaya, told him there was a "smell of terror" in the air.

There are initially no concrete indications of the possible motive for the crime.

According to Ankara, the explosion happened at 4:20 p.m. local time.

At that time, the pedestrian zone was particularly busy.

The street is a tourist hotspot in the center of the European part of the Turkish metropolis, which is often crowded even on Sundays.

A ministry employee and his daughter were among the dead, Family Minister Derya Yanik wrote on Twitter in the evening.

Rescue workers and the police are on site in large numbers, the state broadcaster TRT reported.

Helicopters flew over Beyoglu and neighboring districts in the early evening.

The cause of the explosion was initially unclear.

A powerful bang, followed by flames, can be heard in recordings on the online networks.

The explosion could be heard in neighboring quarters.

The images also show a large, black crater and several people lying on the ground.

According to journalist Ragip Soylu from the Middle East Eye agency, a bag was found in which something may have exploded.

A suspicious woman was also seen on video recordings, he tweeted:

The explosion immediately caused panic among visitors to the shopping street.

The area was immediately evacuated.

People in the city were urged to avoid the area.

Surrounding streets should also be kept free of traffic.

Rescue workers and the police are on site in large numbers, the state broadcaster TRT reported.

Helicopters flew over the Beyoglu district and neighboring districts in the early evening.

Communications Minister Fahrettin Altun said investigations into the background to the crime were ongoing.

Erdogan said footage from surveillance cameras on site would be evaluated.

A woman may have played a role in the attack, he said, without giving details.

The perpetrators would be punished, Erdogan assured.