Blast kills thirteen off-duty soldiers in central Turkish city
At least 55 people were wounded - six in a serious condition - in Saturday's attack in the central Anatolian city of Kayseri, the interior ministry said.
The government said all signs so far suggested the the outlawed Kurdistan Workers Party [PKK] was behind the attack.
Television pictures showed that the bus had been reduced to a smouldering wreck by the impact of the blast, as wounded were taken to waiting ambulances.
Deputy Prime Minister Veysi Kaynak said in televised comments that the attack in Kayseri was "unfortunately similar" to last weekend's strikes in Istanbul.
"All indications at present point to the PKK," Deputy Prime Minister and government spokesman Numan Kurtulmus told NTV television.
"We have to take into account all possibilities but the signs at present point to the PKK."
Prime Minister Binali Yildirim said that the attack was carried out by a "suicide bomber", without giving further details.
The army said that the bus - carrying low-ranking privates and non-commissioned officers - was attacked after leaving the commando headquarters in the city.
The bus was owned by the municipal transport authorities in Kayersi but was transporting the soldiers who had taken permission to go to a local market for the day, the Dogan news agency said.
The explosion comes a week after 44 people were killed on 10 December in a double bombing in Istanbul after a football match. The attack was claimed by Kurdish militants.
|A double bombing near Besiktas Vodaphone Arena last week killed 44 people [Getty]|
'Pay a heavy price'
Turkey has seen a spate of deadly bombings in a bloody 2016 blamed both on Islamic State group and Kurdish militants that have left dozens dead and put the country on daily alert.
In June, 47 people were killed in a triple suicide bombing and gun attack at Istanbul's Ataturk airport, with authorities blaming the Islamic State group.
Another 57 people including 34 children were killed in August in a suicide attack by an IS-linked bomber at a Kurdish wedding in the southeastern city of Gaziantep.
Kurdish militants have twice struck with bombings that killed dozens in Ankara in February and March.
The attacks have come with the civil war still raging in neighbouring Syria, where Turkey is staging its own incursion to force jihadi and Kurdish militias from the border area.
Turkey is also still reeling from a failed 15 July coup blamed on the US-based Islamic preacher Fethullah Gulen that has been followed by a relentless purge of his alleged supporters from all state institutions.
One of the main cities of central Turkey, Kayseri is a key industrial hub with a population of over one million and usually seen as a peaceful area.
It is well west of the southeast of the country that has been hit by months of deadly fighting between the outlawed Kurdistan Workers Party [PKK] and the security forces.
There was no immediate indication of who was behind the latest attack.
The government slapped a temporary broadcast ban on footage of the attack, as is becoming typical in the aftermath of major incidents in the country.
The Turkish military has stepped up operations against the PKK after a fragile ceasefire broke down in the summer of 2015. Since then, there has been a dramatic surge in violence that shows no sign of ending.
Last week's double bombing in Istanbul, which targeted police after a match of the Besiktas football club, was claimed by the Kurdistan Freedom Falcons seen as a radical offshoot of the PKK.
The attack in Istanbul prompted a sharp response from Erdogan, who vowed Ankara would "fight the scourge of terrorism right to the end".
"They should know that they will not get away with it... They will pay a heavier price."