A suicide bombing has left at least five people dead in a busy shopping area popular with tourists and locals in Istanbul.
The governor of Istanbul Province, Vasip Sahin, initially said four people had been killed and 20 people injured in the attack in Ä°stiklal Avenue, also known as Istiklal Street.
But the death toll rose under an hour later as another victim died of their injuries in hospital.
Three Israelis were among the wounded, the country’s foreign ministry said, but nationalities of the other victims were not immediately confirmed.
CCTV footage of the explosion showed shoppers milling around on the street when the bomb was detonated next to a group of people standing on the pavement.
People could be seen lying motionless on the floor as survivors ran for cover.
The wide pedestrianised avenue is one of the most famous streets in Istanbul, lined with boutiques, art galleries, theatres, cafes and foreign consulates, leading to Galatasaray Square.
Local residents said the area hits its peak on weekends afternoon and evenings and that 11am local time (9am GMT), when the blast hit, would have been comparatively quiet.
Growing speculation that the blast was another terror attack aimed at hitting Turkey's tourist industry and liberal social scene could not be confirmed and there was no immediate claim of responsibility.
Turkish authorities reportedly imposed a temporary broadcast ban governing coverage of the attack on Saturday, while Facebook and Twitter were also blocked. The measures are frequently imposed after terrorist attacks in the country.
A spokesperson for the Foreign and Commonwealth Office said officials were monitoring the situation but could not yet confirm whether any British nationals were injured.
It had previously warned of a high threat from terrorism in Turkey, saying that attacks from a range of Islamist and Kurdish groups could be indiscriminate and target areas frequented by foreigners.
There has not yet been any update to the UK Government's travel advice for the country but Germany issued a bulletin advising citizens to stay inside their hotels.
Saturday's explosion came after a bombing claimed by a Kurdish militant group killed 37 people in Ankara on Sunday and a suspected Isis suicide bomber killed 13 tourists at Istanbul's Sultanahmet Square in January.
Both factions have committed atrocities in Turkey at an increasing rate over the past year as Turkey continues military operations in Kurdish areas in the south-east and the Syrian war rages over the border.
Germany closed its embassy in Ankara and a consulate and German school in Istanbul last week because of a warning over an imminent attack.
Both the Istanbul school and consulate are situated near Istiklal Street but it was unclear if the threat was linked to Saturday's attack.
Turkey has been heightening security in the city and Ankara in the run-up to a Kurdish spring festival of Newroz on 21 March, which Kurds in Turkey traditionally use to assert their ethnic identity and demand greater rights.