Four people were killed and dozens injured in a suicide bomb attack in a busy shopping street in Istanbul.
The explosion went off on Istiklal Street, near a government building, at around 11am on Saturday morning.
Noone has yet claimed responsibility for the attack but the Turkish government is blaming the so-called Islamic State (IS).
Both IS and Kurdish militants have claimed recent attacks in Turkey.
Earlier this month, 35 people were killed by Kurdish militants in Ankara, the Turkish capital.
In February, 28 were killed when a military convoy was targeted, also in Ankara.
In January, 12 German tourists were killed in a suspected IS suicide bombing in Istanbul and last October more than 100 people were killed in a double suicide bombing at a Kurdish peace rally in Ankara.
Updating its advice following Saturday’s explosion, the UK Foreign and Commonwealth Office told British citizens to avoid the area and follow instructions given by Turkish security forces.
Minister for Europe David Lidington said he was appalled to hear of another ‘senseless’ bomb attack in Turkey.
"I extend my deepest condolences and sympathies to the families and friends of those killed or injured in Istanbul. The UK stands side by side with its Turkish friends at this difficult time and offers any assistance that may be required to track down those responsible. With unity, calm and determination, we can defeat the menace of terrorism."
