Two car bombs exploded near the Turkish border with Syria on Saturday, killing at least 40 people and injuring scores more in the town of Reyhanli.
"Two cars exploded in front of the municipality building and the post office in Reyhanli," Interior Minister Muammer Guler said in comments on Turkish television.
Reyhanli, in the southern Hatay province, is in an area known to be home to many refugees. There are more than 300,000 Syrian refugees in Turkey, most of them in camps along the volatile border.
President Bashar Assad's administration was the "usual suspect" in the attacks, Turkish Deputy Prime Minister Bulent Arinc said.
"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."
There was no immediate claim of responsibility. Nor was there any comment from Damascus.
Turkey PM: Red line has been crossed
Speaking to reporters during a visit to Berlin, Turkey's Foreign Minister Ahmet Davutoglu said the country would protect itself if threatened.
Turkey supports the uprising against beleaguered Assad and has been a vocal critic against the regime.
"There may be those who want to sabotage Turkey's peace, but we will not allow that," he said. "No one should attempt to test Turkey's power; our security forces will take all necessary measures."
The United States condemned the attacks and vowed solidarity with Turkey in identifying those responsible.
"The United States condemns today's car bombings and we stand with our ally, Turkey," read a statement from Secretary of State John Kerry. "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 center of my work as Secretary of State these last three months. Our thoughts are with the wounded and we extend our deepest condolences to the families of the victims."
"The United States strongly condemns today's vicious attack, and stands with the people and government of Turkey to identify the perpetrators and bring them to justice," U.S. Ambassador to Turkey Francis Ricciardone said in a statement.
NBC News Correspondent Richard Engel and Reuters contributed to this report.
