Scuffles have broken out in the Turkish capital as police prevented pro-Kurdish politicians and other mourners from laying flowers at the site of two suspected suicide bombings that killed 95 people in the country's deadliest attack in years.

Turkey declared three days of mourning following Saturday's near-simultaneous explosions in Ankara that targeted a peace rally attended by activists, labour unions and members of the pro-Kurdish party.

The party's co-leaders, Selahattin Demirtas and Figen Yuksekdag, planned to hold a memorial for the victims but they were held back by police who insisted investigators were still working at the site.

There was no immediate claim of responsibility for the attacks, but Prime Minister Ahmet Davutoglu said Kurdish rebels and Islamic State (IS) militants were the most likely culprits.

The two explosions occurred seconds apart outside the capital's main train station as hundreds of opposition supporters and Kurdish activists gathered for the peace rally. The protesters planned to call for increased democracy in Turkey and an end to the renewed violence between Kurdish rebels and Turkish security forces.

The attacks came at a tense time for Turkey, a Nato member that borders war-torn Syria, hosts more refugees than any other nation in the world and has seen renewed fighting with Kurdish rebels that has left hundreds dead in the last few months.

Many people at the rally had been anticipating that the rebels of the Kurdistan Workers' Party, or PKK, would declare a temporary ceasefire - which they did hours after the bombing - to ensure that Turkey's November 1 election would be held in a safe environment.

Television footage showed a line of protesters near Ankara's train station, chanting and performing a traditional dance with their hands locked, when a large explosion went off behind them.

"There was a massacre in the middle of Ankara," said Lami Ozgen, head of the Confederation of Public Sector Trade Unions.

One report said the attacks were carried out with TNT explosives fortified with metal ball-bearings.

At least 248 people were injured in the blasts, and 48 of them are said to be in a serious condition.

Turkish police have detained 14 suspected members of IS in the central city of Konya.

The group, which included a woman, was held following simultaneous raids to homes.

It is not yet clear if the detentions are related to the twin blasts in Ankara.

At the Vatican, Pope Francis led followers in silent prayer for the victims of what he described as the "terrible slaughter" in Ankara.

The Pope paused for 30 seconds of silent prayer for "that dear country" during his traditional Angelus blessing.

He told followers gathered in St Peter's Square that news of the Ankara bomb attacks brought "pain for the numerous dead, pain for the wounded and pain because the attackers hit helpless people who were demonstrating for peace".