A car bomb has torn through a crowded transport hub in the Turkish capital Ankara, killing at least 34 people and wounding 125 in the second such attack in the administrative heart of the city in under a month.
The blast, which could be heard several kilometres away, sent burning debris showering down over an area a few hundred metres from the Justice and Interior Ministries, a top courthouse, and the former office of the Prime Minister.
"These attacks, which threaten our country's integrity and our nation's unity and solidarity, do not weaken our resolve in fighting terrorism but bolster our determination," President Tayyip Erdogan said in a statement.
Two senior security officials told Reuters the first findings suggested that the Kurdistan Workers Party (PKK), which has waged a three-decade insurgency for Kurdish autonomy, or an affiliated group were responsible.
There was no immediate claim of responsibility, but Interior Minister Efkan Ala said the group would be named after initial investigations were completed.
"Tonight, civilian citizens waiting at a bus stop were targeted in a terrorist attack with a bomb-laden car," Mr Ala told reporters after a meeting with Prime Minister Ahmet Davutoglu, the head of the intelligence agency and security chiefs.
NATO member Turkey faces multiple security threats.
As part of a US-led coalition, it is fighting Islamic State in neighbouring Syria and Iraq. It is also battling PKK militants in its southeast, where a two-and-a-half year ceasefire collapsed last July, triggering the worst violence since the 1990s.
The bombing came two days after the US embassy issued a warning of a potential attack on government buildings in the Bahcelievler area of Ankara, just a few kilometres away from the blast site.
Health Minister Mehmet Muezzinoglu said 30 of those killed had died at the scene, while the four others died in hospital and that at least one or two of the dead were attackers.
One security official said the car used in the attack was a BMW driven from Viransehir, a town in the largely Kurdish southeast, and that the PKK and the affiliated Kurdistan Freedom Hawks (TAK) appeared to be responsible.
TAK claimed responsibility for the previous car bombing, just a few blocks away, on February 17, which killed 29.
A police source said there appeared to have been two attackers, one a man and the other a woman, whose severed hand was found 300 metres from the blast site.
The explosives were the same kind as those used on February 17 and the bomb had been reinforced with pellets and nails to cause maximum damage, the source told Reuters.
World leaders condemned the bombing.
British Prime Minister David Cameron said he was "appalled," while French Foreign Minister Jean-Marc Ayrault described it as a "cowardly attack".
Russian President Vladimir Putin described it as "inhuman", his spokesman Dmitry Peskov said.
The Australian government won't be pulling diplomatic staff out of Turkey.
Australia's ambassador to Turkey James Larsen was about 20 metres from the blast. Foreign Minister Julie Bishop says Mr Larsen is "somewhat shaken" but fine, and focused on continuing his job.
She ruled out withdrawing staff at Australia's embassy in Turkey.
"No, we would not," she told reporters in Fiji on Monday.
The government constantly reviewed security arrangements for diplomats posted overseas, she said.
Ms Bishop wasn't aware of any Australians injured or killed in the blast and said all embassy staff are unharmed.
"This is a stark reminder of the fact that terrorist attacks can occur at any time and anywhere," she said. "And that's why Australia is involved in the coalition to defeat terrorism at its source in Syria and Iraq."
Ms Bishop said Australia would be working closely with the Turkish government to ensure Australians travelling to Gallipoli for Anzac Day would be as safe as possible.
"The heightened security will make it very challenging for travellers," she said.
The Department of Foreign Affairs and Trade continues to advise travellers to Turkey to maintain a "high degree of caution".
AAP / Newshub.