Turkish government officials said the blast was a “terrorist attack” and they were investigating claims that a suicide bomber was responsible. A health minister said 86 people had been killed and hundreds more were injured.
The explosions happened as hundreds gathered outside Ankara’s main train station for a peace rally to protest against the conflict between Turkish security forces and Kurdish militants in the southeast.
Witnesses said the two explosions happened seconds apart shortly after 10:00 am (0700 GMT). There were no immediate claims of responsibility for the attack.
“We are faced with a very big massacre, a vicious, barbarous attack,” pro-Kurdish opposition leader Selahattin Demirtas told reporters.
The attacks come three weeks ahead of a parliamentary election in Turkey and at a time of multiple security threats, not only in the restive southeast but also from Islamic State militants in neighbouring Syria and home-grown leftist militants.
Prime Minister Ahmet Davutoglu cancelled his next three days of election campaigning and was due to hold an emergency meeting with the heads of the police and intelligence agencies and other senior officials, his office said.
Turkey, a Nato member, has been in a heightened state of alert since starting a “synchronized war on terror” in July, including air strikes against Islamic State fighters in Syria and PKK bases in northern Iraq. It has also rounded up hundreds of suspected militants at home.
Designated a terrorist group by Turkey, the United States and the European Union, the PKK launched a separatist insurgency in 1984 in which more than 40,000 people have been killed.
The state launched peace talks with the PKK’s jailed leader in 2012 and the latest in a series of ceasefires had been holding until the violence flared again in July.