"Early indicators would point to ISIS as the culprit," said Soner Cagaptay, director of the Turkish research program at the Washington Institute for Near East Policy. ISIS is a common acronym for the Islamic State.
Either way, "this could well be Turkey's 9/11," Cagaptay said. "This is simply the worst terror attack in Turkish history."
The United States also condemned the twin bombings as a terrorist attack. "It is particularly important at this time that all Turkish citizens recommit to peace and stand together against terror," the State Department said in a statement.
The demonstrators, mobilized by a coalition of Turkish trade unions, had gathered outside Ankara's main station hours earlier to chant, wave banners and flags and call for peace. The crowd included a mix of Kurdish and leftist Turkish activists, local media reports said.
A video circulated on social media showed demonstrators linking arms to perform a traditional dance before a fiery explosion erupted in the background, sending the crowd into a panic. It was unclear whether that explosion was from the first or the second bomb detonated outside the station.
Images from the scene showed dazed and bloody demonstrators clinging to one another in the aftermath of the blasts. Bodies, some of them dismembered, lay on the street, covered with flags protesters had brought to the march.
Tensions between police and demonstrators flared following the explosions, after activists accused security forces of blocking ambulances arriving to treat the injured. Turkey's pro-democracy activists say they are fed up with a state that is quick to crack down on dissenters but cannot keep its own citizens safe from terrorists.
Turkey's health minister said that 62 people died at the scene of the attack Saturday morning and that 24 others died in the hospital. Another 28 people were still in intensive care, the Health Ministry said.
In a live television broadcast, Turkish Interior Minister Selami Altinok said in response to a reporter's question that he would not resign because there had been no security breach.
Still, Turkish authorities announced a news blackout on images showing the moment of each blast, gruesome or bloody images or "images that create a feeling of panic," according to the Associated Press. The agency also reported that social media users in Ankara were unable to access Twitter after the blast.
Turkey, which media watchdog groups say has one of the world's worst records on press freedom, often blocks access to Twitter and other sites for content the government deems inappropriate.
Also Saturday, the militant Kurdistan Workers Party (PKK), a hard-line Marxist organization that has had led the fight for Kurdish autonomy in Turkey, called a temporary cease-fire to calm tensions ahead of general elections scheduled for Nov. 1.
The PKK has been locked in a struggle with the Turkish state for three decades to win more rights - and possibly independence - for Turkey's more than 16 million Kurds. Kurdish communities also live in areas of Iran, Iraq and Syria, where PKK-linked militias have carved out territory and taken on the Islamic State. Some observers say the success of the Syrian-Kurdish militias in seizing land in Syria has worried Turkish officials, who fear it could inspire its own Kurdish minority.
In 2013, the PKK had agreed to withdraw its fighters from Turkish territory to militant hideouts in northern Iraq in exchange for expanded constitutional rights for Kurds. But each side soon accused the other of failing to implement the accords, and violence flared again this summer. PKK militants attacked Turkish troops and security installations, particularly in the country's volatile southeast. Turkey launched an air campaign against PKK positions in northern Iraq, killing scores, the militants said.
"I think with the attack (on Saturday), the perpetrators are hoping to induce the PKK, or its rogue and more radical youth elements, to continue fighting Turkey," Cagaptay said.
In Suruc in August, Turkish authorities rounded up dozens of young Kurdish men they accused of belonging to the PKK's youth wing. The families of the detainees said they had all voted for the pro-Kurdish People's Democratic Party (HDP) in legislative elections in June and accused the Turkish government of punishing Kurds for gaining the party about 12 percent of the vote.
The same polls denied the ruling party of President Recep Tayyip Erdogan a governing majority for the first time since 2002. The results stunned the president's Justice and Development Party (AKP), which subsequently failed to form a coalition government.
In August, Erdogan called the snap November polls. Critics say he hopes the elections will deliver his party the majority it needs to expand his presidential powers.
"Even if violence spirals up again, the attack will likely have a minimal impact on the election outcome," Cagaptay said.
"Polarization over Erdogan trumps other concerns in Turkey," he said
