At least 31 people were killed in the explosion -- one of the deadliest terrorist attacks to rock the country in years. At least 100 others were wounded, provincial Gov. Izzettin Kucuk told Turkish media.
Crowds of mourners wept and chanted beside flag-draped coffins as the funerals got underway.
Suruc lies about 6 miles from the Syrian border opposite Kobani, the Syrian city that was the scene of intense fighting last fall between ISIS
and predominantly Kurdish forces, backed by coalition airstrikes.
Turkish Prime Minister Ahmet Davutoglu told a news conference Tuesday that "one suspect has been identified" and that all that person's "links domestically and internationally are being investigated."
"Right now links to ISIS and it being a suicide bomber have gained probability," he said. "We expect the investigation to be completed as soon as possible."
Davutoglu on Monday described ISIS as "not just a threat to Syria but to Turkey as well."
He urged solidarity among the Turkish people, saying the attack was not against any one part of the country but "against all of us."
Davutoglu said the government would not hesitate in taking action in response to the bombing, which he suggested was in revenge for the role Turkey is playing in the war on terror.
There was no immediate claim of responsibility for the blast, which struck a gathering of mostly Kurdish activists calling for more help to rebuild Kobani.
Police fire tear gas at Istanbul rally
Late Monday, police fired tear gas and water cannons to disperse several hundred demonstrators gathered in Istanbul, Turkey's largest city, to show support for the victims of the blast.
The explosion occurred at midday at the Amara Cultural Park in Suruc, where an activist group had gathered.
Photos and video from the scene show bodies strewn around a park and dazed people at the blast site while emergency teams rush to aid victims.
"Kids were screaming, everyone was screaming and running," eyewitness Erhan Subasi told CNN. "Everyone was in a panic but trying to help.
"People's faces were blown off, arms scattered. ... You could smell burned bodies."
The mood in the town was somber as investigative and forensics teams worked into the night, blood still staining the ground.
On Tuesday, toys appeared at the scene of the bombing, placed in a symbolic reference to the playthings that some of those targeted had been sending into devastated Kobani.
The Kurdish and Syrian rebel forces eventually succeeded in driving ISIS out of the strategic stronghold, but the Syrian town was left in ruins.
President urges 'global effort' against terrorism
It's not the first time the violence in Syria has spilled over into Turkey. But the scale of this attack against Kurds on Turkish soil will doubtless raise fresh questions over how the government is handling the ISIS threat.
A Turkish official speaking on condition of anonymity told CNN on Monday that the government thinks the attack is "retaliation to the Turkish government's fight against terrorism."
The official called for the international anti-ISIS coalition to "more actively pursue a solution to the crisis in Syria
Turkish President Recep Tayyip Erdogan condemned the attack.
"Terror doesn't have a nation, race or homeland," he said. "That is why we have been consistent in underlining the need for a global effort to fight terror."