A 20-year-old Turkish student has been identified as the suicide bomber who killed 32 youth activists in the town of Suruc on Monday, officials say.
The attacker, named by local media as Seyh Abdurrahman Alagoz, was an ethnic Kurd from Turkey's south-eastern province of Adiyaman and reportedly had links to Islamic State (IS) militants.
Meanwhile, Kurdish militants say they killed two Turkish police officers.
The PKK said it was in revenge for the deaths in Suruc, a mainly Kurdish town.
Turkish officials have blamed the Suruc attack on IS. But many in Turkey feel the government has not done enough to support the Kurds in their fight to combat the threat of IS militants across the border in Syria - something denied by Ankara.
There have been rallies in cities across the country, with people condemning the attack and protesting at the government's policies on Syria.
Access to Twitter was briefly blocked on Wednesday after a court banned the publication of images from the massacre in Suruc.
But some critics have accused the government of trying to stop Twitter users from continuing to organise further protests.
Added tensions - Jim Muir, BBC News, Urfa, southern Turkey
The claim by the PKK's military wing that it carried out the killing of two Turkish policemen in Celanpinar is an ominous development, coming as it does two years into a supposed truce between the Kurdish militants and the Turkish security forces.
Hopes for a resolution of Turkey's long-running dispute with its own Kurds have slowly dimmed since the imprisoned PKK leader Abdullah Ocalan called on Kurdish fighters to pull out of Turkey into bases in northern Iraq.
The deal for the recognition of Kurdish rights in Turkey was never really carried through by President Erdogan, whose AK party failed to retain its majority in recent elections and is now seeking coalition partners.
The suicide bomb attack on a group of youth activists in Suruç on Monday, killing 32, has clearly aggravated tensions, leading to angry demonstrations and clashes between pro-Kurdish protestors and riot police.
The killing of the two policemen in "revenge" for the Suruc bomb will add to the tension.
Turkish authorities said DNA tests had confirmed that the Suruc bomber was a 20-year-old man of Kurdish origin born in Adiyaman.
Seyh Abdurrahman Alagoz's mother told the newspaper Radikal (in Turkish) that her son was a former student at Adiyaman university who had gone "abroad" six months ago with his brother.
"I don't know what they were doing abroad, they never said. They were just telling me they were fine," Semure Alagoz said.
A senior Turkish official told Reuters that he believed the bomber, who he did not name, had travelled to Syria last year with the help of a group linked to IS militants.
Monday's suicide bombing claimed 32 lives and injured 100 others, making it one of the deadliest attacks in Turkey in recent years.
The activists were mainly university students, who were holding a news conference when an explosion ripped through the Amara Cultural Centre.
They had been planning to travel to Syria to help rebuild the town of Kobane. The youngest victim was Okan Pirinc, who was 18, according to the Turkish media.
On Wednesday, two Turkish police officers were found shot dead in their home in the town of Ceylanpinar, which is in the same province of Suruc and close to the Syrian border.
The military wing of the outlawed Kurdistan Workers' Party (PKK) claimed responsibility for the killings in a statement on its website.
"Today, around 06:00, a revenge operation was carried against two policemen collaborating with daesh (IS)," it said.