Turkey says it will take necessary measure to protect itself after two car bombs killed at least 43 people in a town on its border with Syria.
Turkish Foreign Minister Ahmet Davutoglu vowed to catch those behind the attack in Reyhanli which is home to many Syrian refugees. "Nothing will go unanswered," Mr Davutoglu said.
Turkey, a member of Nato, said it suspected the involvement of a Syrian intelligence agency.
But Syria denied it was responsible.
Turkey is a strong supporter of the opposition in Syria's civil war and a vocal critic of the government of President Bashar al-Assad.
The US and Nato have condemned the bombs and expressed support for Ankara.
Speaking during a visit to Berlin, Mr Davutoglu said it was "not a coincidence" that the bombings occurred as diplomatic efforts to solve the Syrian crisis were intensifying.
"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."
However, he said he saw no reason to call an emergency meeting of Nato. Such a meeting would be the first step towards involving the alliance in any possible response.
Deputy Prime Minister Besir Atalay said he believed the attackers were from Turkey but linked to a Syrian intelligence agency.
"We have established that the organisation and assailants have links to the pro-regime Mukhabarat (intelligence) organisation," he told reporters.
He did not name the group but said the attack was intended to pit Turks against Syrian refugees in Reyhanli.
But Syrian Information Minister Omran al-Zoubi told a news conference on Sunday, "No-one has the right to make false accusations."
"Syria did not commit and would never commit such an act because our values would not allow that," he said.
BBC World Affairs correspondent James Reynolds says the attacks will put pressure on Turkish Prime Minister Recep Tayyip Erdogan.
His policy on Syria has always been to support the Syrian opposition but not become involved in the war, but the attacks now make it very difficult for him to carry on staying out of the conflict, our correspondent adds.
Mr Erdogan travels to Washington in a few days time for long-planned talks with President Barack Obama.
Reyhanli is an entry point for refugees fleeing violence in Syria and local people attacked Syrian refugees and cars with Syrian number plates after the attack, according to local media.
The bombs exploded 15 minutes apart near the town hall and post office catching many passers-by.
Video posted on Turkish media showed people running to help victims of the first blast when the second explosion was heard.
The border area of Reyhanli has itself been attacked in recent months.
In February, an explosion near the town killed 17 people and wounded 30.
Five people were killed last October when a mortar round hit the Turkish border town of Akcakale.