The Turkish government has vowed to increase security along its border with Syria after a suicide bombing killed at least 32 people in the Kurdish town of Suruc.
The explosion occurred in the middle of day outside a cultural centre just six miles from the Syrian border, injuring around 100 people.
Turkish authorities say they have identified the suspected attacker and their links to local and international groups are being investigated. The attack was "retaliation for the Turkish government's efforts to fight terrorism," said one senior official.
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The government believes it was carried out by a suicide bomber with links to Islamic State, although the terrorist group has yet to claim responsibility for the massacre.
President Recep Tayyip Erdogan condemned the bomb attack and those "who conducted this brutality". "Terror has no religion, no country, no race," he said.
If Islamic State's role in the bombing is confirmed, it would be one of the group's deadliest strikes on Turkish soil to date, the Daily Telegraph reports.
The majority of the victims were young student activists who were going to deliver aid to the nearby Syrian town of Kobane, which Kurdish fighters regained from Islamic State militants last year.
They had planned to travel to Kobane to deliver toys, plant a memorial forest, as well as build a library and a playground, The Guardian reports.
The attack prompted widespread protests in Istanbul, with demonstrators blaming the government for not doing enough to protect the Kurdish population along the Syrian border.
The bloodshed could prompt the Turkish government – which remains reluctant to get involved in the bombing of IS targets in Syria and Iraq – to take action against the extremists, analysts told the Financial Times.
"Ankara cannot afford to let down its guard regarding IS otherwise this could spiral into a Turkish conflict," warned Nigar Goksel, senior Turkey analyst at International Crisis Group.
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