Four people were killed and 36 wounded in a suicide bombing in Istanbul's main shopping district on Saturday.
A widespread state of fear has begun to seep across Turkey, which has suffered from four major attacks since the start of the year.
The latest, a bombing in the popular city of Istanbul, killed an Iranian and three Israelis - two with dual Israeli-US nationality.
It also injured nationals from Germany, Ireland, Iceland and the United Arab Emirates.
The bomber - a Turkish national - was also killed, and has been named by Turkish authorities as 24-year-old Mehmet Ozturk.
Turkey's Interior minister, Efkan Ala, says the man belonged to IS, also known as Daesh.
"Our findings show that the terrorist is affiliated with terrorist organisation Daesh. It is being investigated whether he has other connections or whether there are other powers (involved). The information I received was there was not a warrant issued for this person by police or gendarmarie. So far, five people were detained regarding this matter."
Turkish authorities have since postponed a football match in Istanbul amid fears of a repeat attack, as security dramatically increased across the country.
Some public celebrations for the Persian new year holiday of Newroz were also cancelled.
Meanwhile, the bodies of the slain Israelis have been returned to Israel.
Rafael Strugo, from Israeli rescue service Magen David Adom, says a further ten of those injured were Israeli nationals.
"We brought home all the ten wounded and the three casualties. From the ten wounded patients, five of them were lightly wounded, they came back last night. The other five, in a complex cooperation of Magen David Adom and the Israeli Defense Force, we brought them back home today."
Turkey is part of the United States-led coalition against IS and allows coalition planes to use its air bases for raids on Iraq and Syria, which has seen a major retaliation from the terror group.
Prior to Saturday's blasts, its most recent attack was in January when another suspected IS suicide bomber killed 12 German tourists, also in Istanbul.
But other deadly assaults have also been launched by other groups: Kurdish separatists the PKK claimed responsibility for a blast in the capital, Ankara, last week which killed 37 people.
Turkey's death toll from such attacks in 2016 has exceeded 80 people, much to the dismay and anger of President, Recep Tayyip Erdogan.
President Erdogan has told a packed crowd that Turkey will "never surrender to terror".
"The terror groups and the forces behind them will in the end be defeated. Our security forces are - and will be - working hard to prevent the terror organisations' acts and will continue to do so."
There's anger too from Israeli Prime Minister, Binyamin Netanyahu, who says his government and military stand at the "front of the battle" against world terror.
"I think this brings to light the fact that we're all subject to terrorist onslaughts. Terrorism, international terrorism, Islamist terrorism is now attacking the countries of the Middle East and the countries beyond the Middle East. Its scope is international, the response to it should be international."
