The Turkish government has promised to increase security on the country's border with Syria after 30 people were killed and over 100 wounded in a bombing yesterday in the town of Suruc.
Investigators think the blast was caused by a female suicide bomber from the Islamic State group.
The attack triggered violent protests in Istanbul, with police using water cannon, teargas and rubber bullets.
Its thought that those killed were mostly students who were about to cross into Syria to to take part in relief work in Kobane.
Turkish President Tayyip Erdogan called the bombing a "terrorist attack" and the government said security measures along the country's border with Syria would be stepped up.
Video shown on local television of the moments before the explosion showed a large group of people standing behind a Socialist Youth Associations Federation (SGDF) banner before it is ripped apart by the huge blast.
Many victims were university-aged students.
Prime Minister Ahmet Davutoglu told a news conference in Ankara that 30 people had been killed and that the blast was "most probably a suicide bombing".
"Turkey has taken and will continue to take all necessary measures against Islamic State," Mr Davutoglu said.
"Measures on our border with Syria ... will be increased."
Pervin Buldan, a lawyer from the pro-Kurdish HDP opposition party, said Turkish and Kurdish youths had gathered at the centre ahead of a planned trip to Kobane to take part in relief work.
Kobane had recently been secured by Syrian Kurdish fighters last month following an unsuccessful attack by militants from Islamic State (IS) who surrounded the town but were repelled by Kurdish forces and Free Syrian Army rebels.
Pictures posted on Twitter after the blast showed bodies covered with newspapers.
"I saw more than 20 bodies. I think the number of wounded is more than 50. They are still being put into ambulances," one witness said.
"It was a huge explosion, we all shook."
A Turkish official said Islamic State appeared to have been responsible and that the attack was a "retaliation for the Turkish government's efforts to fight terrorism".
The explosion comes weeks after Turkey supplied extra troops and resources along part of its border with Syria, over fears of an increase in fighting between Kurdish forces, rebel groups, Syrian government troops and IS.
The White House condemned the attack, calling it "heinous". A spokesperson said, "we express our solidarity with the Turkish government and the Turkish people and reaffirm our undeterred resolve to the fight against the shared threat of terrorism."
