Twin explosions outside the main train station in the Turkish capital Ankara killed at least 95 people and wounded hundreds of others at a peace rally on Saturday, in what government officials described as a terrorist attack.
Authorities were investigating claims the attacks were carried out by a suicide bomber, two government officials told Reuters. Prime Minister Ahmet Davutoglu was due to hold an emergency meeting with the heads of the police and intelligence agencies and other senior officials, his office said.
Turkey's government says it has imposed a temporary news blackout following the attack, Turkey's deadliest in recent years.
A government spokesman said the blackout Saturday covered images showing the moment of the blast, gruesome or bloody images or "images that create a feeling of panic."
He warned media organizations they could face a "full blackout" if they did not comply.
On Saturday, many people in Ankara reported being unable to access Twitter and other social media websites after the blasts. It was not clear if authorities had blocked access to the websites.
Turkey frequently imposes blackouts following attacks.
Witnesses said the two explosions happened seconds apart shortly after 10:00am (0700 GMT) as hundreds gathered for a planned "peace" march to protest against the conflict between Turkish security forces and Kurdish militants in the southeast.
Violence between the state and the Kurdistan Workers Party (PKK) militants has flared since July, when Turkey launched air strikes on militant camps in response to what it said were rising attacks on the security forces. Hundredshave since died.