Turkey has accused groups supporting the Syrian regime of carrying out two car bombings that killed at least 46 people and injured dozens in a border town, the interior minister said.
The blast occurred on Saturday in a crowded area of the small town of Reyhanli in the southern Turkish province of Hatay, just a few kilometres from the main border crossing into Syria.
The interior minister told Al Jazeera that 55 people had been hospitalised, including seven Syrians. The majority of the victims were Turkish nationals.
"There is a mood of devastation here," Al Jazeera's Andrew Simmons reported from Reyhahli.
Bulent Arinc, the deputy prime minister of Turkey, said investigators had established links between an intelligence agency of Syrian President Bashar al-Assad and the deadly car bombs.
"We know that the people taking refuge in Hatay have become targets for the Syrian regime," Arinc said in comments broadcast on Turkish television.
"We think of them as the usual suspects when it comes to planning such a horrific attack."
Ahmet Davutoglu, the foreign minister, said Turkey reserved the right to take "every kind of measure" after the attacks.
"The attack has nothing to do with the Syrian refugees in Turkey, it's got everything to do with the Syrian regime," Davutoglu told Turkey's TRT television on Sunday.
He said those behind the bombings were believed also to have been behind an attack on the Syrian coastal town of Banias a week ago, in which fighters backing Assad were reported to have killed at least 62 people.
The Syrian information minister, however, denied responsibility for Turkey blasts on Sunday, saying that Turkey was indirectly responsible.
"Syria did not commit and would never commit such an act because our values would not allow that," Omran al-Zohbi said at a news conference broadcast by state television.
Ban Ki-moon, the UN chief, and US Secretary of State John Kerry both strongly condemned the bombings.
Kerry said in a written statement that US stood by its ally, Turkey.
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"This awful news strikes an especially personal note for all of us given how closely we work in partnership with Turkey, and how many times Turkey's been a vital interlocutor at the centre of my work as secretary of state these last three months," Kerry said.
UN spokesman Martin Nesirky said that Ban "condemns all acts of terrorism and reiterates that no cause or grievance ever justifies the targeting of civilians".
A third, smaller explosion caused panic in Reyhanli hours after the twin car bombs struck, but NTV quoted Muammer Guler, the interior minister, as saying that it was unrelated and occurred when a car's fuel tank exploded.
The area has been caught up in violence spilling over from the Syrian side in the past few months.
Reyhanli is home to many of the more than 300,000 refugees who have sought shelter from the uprising against Assad which erupted in Syria in March 2011.
The blasts came as Syrian troops fought rebels in a bid to take back a key supply route linking the centre of the country to Aleppo in the north, an activist group said.
"Fierce battles raged pitting troops against rebels. Regime troops fought to reopen the road linking Hama to Aleppo," Rami Abdul Rahman, the director for the London-based Syrian Observatory for Human Rights, told the AFP news agency.
Rebels cut off the road, referred to as the Desert Road, on Thursday. The army had been using it as its main supply route to Aleppo province, large swathes of which are under rebels' control.