A suicide attacker detonated a bomb on Istanbul's main pedestrian shopping street on Saturday, killing five people, the city's governor said.
Twenty other people were injured in the attack.
The attacker was among the dead.
Governor Vasip Sahin said the explosion occurred outside a local government office on Istiklal Street, which is also home to cafes, restaurants and foreign consulate buildings.
Sahin said one of wounded victims died in hospital.
The private Dogan news agency said at least three of the injured are Israeli nationals.
Police sealed off the area and a forensic team was at the scene.
Turkey was already on edge following two recent suicide car bomb attacks in the capital, Ankara, which were claimed by a Kurdish militant group, which is an off-shoot of the outlawed Kurdistan Workers' Party, or PKK.
The most recent attack, on March 13, targeted a line of bus stops on Ankara's busiest street and killed 37 including two bombers.
"It was one loud explosion," said Muhammed Fatur, a Syrian who works at a butcher shop near the scene of Saturday's explosion.
"Police came to the scene and sealed off the area."
Turkey had heightened security in Ankara and Istanbul in the run-up to a Kurdish spring festival of Newroz on March 21, which Kurds in Turkey traditionally use to assert their ethnic identity and demand greater rights.
The Ministry of Foreign Affairs and Trade's Safe Travel Website advises there is "some risk" to security in Turkey due to the heightened threat of terrorism and the potential for civil unrest.
It advises New Zealanders take caution in the country and says there is a significant threat from terrorism.
"Terrorist attacks have been regularly carried out in the south-east; more recently attacks have occurred in Ankara and Istanbul, and could occur in other parts of the country, including, Izmir, Adana, other major centres, tourist areas and along the Mediterranean and Aegean coasts."
For more information go to https://www.safetravel.govt.nz/turkey
Recent incidents in Turkey include:
• On March 13, 2016, an explosion in the Kizilay district in central Ankara killed 37 people and injured many more.
• On February 17, 2016, a large explosion in central Ankara killed 28 people. The attack appeared to specifically target military personnel.
• On January 12, 2016, a suicide attack in the Sultanahmet tourist district of Istanbul killed twelve foreign nationals and injured a number of others.
• On December 23, 2015, a mortar attack which killed one person was conducted at Sabiha Gökçen Airport, Istanbul's second largest airport, by the Kurdistan Freedom Falcons (TAK).
• On October 10, 2015, an attack on a political rally outside the main railway station in Ankara killed 102 people.
- AP and NZ Herald