At least 27 people have been killed in a suspected Islamist suicide bombing attack against a group of young political activists in a south eastern Turkish city near the Syrian border on 20 July, authorities said.
The Turkish government described the large explosion that hit a cultural centre in Suruc, on the opposite side of the border from the embattled Syrian city of Kobani, as a "terrorist attack".
"We call on everyone to stay united in the face of this terrorist attack targeting our country's unity," the interior ministry said in a statement.
Although no group has yet claimed responsibility for it, fingers have been pointed at the Islamic State (Isis).
"Our initial evidence shows that this was a suicide attack by IS," Reuters quoted a senior official as saying.
Another official, speaking on condition of anonymity, told AP they suspected a suicide bomber triggered the blast.
The interior ministry said almost 100 people have been injured and were being treated at local hospitals.
Many of the victims were members of a socialist youth group who had been staying at the culture centre after volunteering for a summer expedition to help rebuilt Kobani, which was left ravaged by months of fighting between Kurdish fighters and IS militants, according to Hurriyet Daily News.
No long before the explosion Federation of Socialist Youth Associations posted a picture of smiling youth workers gathered around a long table in the centre's garden on Twitter.
The account later tweeted photos of numerous severely burnt bodies scattered across the same garden, some covered by newspapers.
The moment of the blast was also captured on camera, with online footage showing a group of activists shouting slogans and holding banners before being wiped out by a massive explosion.
Distraught onlookers and survivors could be heard crying for help in another online clip showing the aftermath of the attack.