Turkey's foreign minister has blamed the world's inaction on the Syrian conflict for the "barbarian act of terrorism" that claimed dozens of lives near the border.
Ahmet Davutoglu's comments in Berlin came a day after a twin bombing in the small town of Reyhanli, in the southern Turkish province of Hatay bordering Syria, that left at least 46 people dead and 100 others wounded.
They also followed a vigorous denial by Syria of any links to Saturday's blasts - the deadliest incident on Turkish soil since the Syrian conflict began.
Holding Turkey indirectly responsible for the blasts, which took place just a few miles from the main border crossing into Syria, Omran al-Zoubi said: "Syria did not commit and would never commit such an act because our values would not allow that."
Turkey has taken in more than 400,000 Syrian refugees, many of whom have settled in Hatay, and has thrown its full weight behind the armed opposition fighting to overthrow Assad, although it denies supplying weapons.
Fighters are able to cross back and forth across the frontier virtually unchallenged, unsettling many on the Turkish side of the border, who say more and more radical groups are joining the opposition ranks.
Davutoglu had earlier told Turkey's TRT television that he did not believe the attacks were linked to Syrian refugees in his country, but that they had "everything to do with the Syrian regime".
In-depth coverage of escalating violence across Syria
Besir Atalay, Turkey's deputy prime minister, said authorities had arrested nine people, all Turkish citizens and including the alleged mastermind of the attacks.
The developments came as hundreds of protesters took to the streets of Antakya, about 50km from the Syrian frontier, on Sunday.
Several hundred people, mostly leftist and nationalist demonstrators, marched through the centre of the city, carrying banners and shouting anti-government slogans while onlookers cheered.
In a speech in Istanbul later broadcast on state TV, Recep Tayyip Erdogan, Turkish prime minister, said: "We will not lose our calm heads, we will not depart common sense, and we will not fall into the trap they're trying to push us into."
But he added: "Whoever targets Turkey will sooner or later pay the price."
Davutoglu, for his part, called the blasts a breach of Turkey's "red line" and said that "it's time for the international community to display a common stance against the regime ... immediately and without delay".
He called for an "urgent, result-oriented diplomatic initiative" to find a solution to the Syrian crisis and said that "Turkey has the right to take any kind of measure" in response to the killings.
Germany pledges support
During his talks with Davutoglu, Guido Westerwelle, the German foreign minister, expressed his condolences for the victims of the "barbaric act of terrorism" and pledged his country's support for Turkey.
Muammer Guler, Turkey's interior minister, said the bombings were carried out by a group with direct links to Syria's intelligence agency.
Davutoglu specifically blamed "a former Marxist organisation directly connected with the regime" of Syrian President Bashar al-Assad.
He also said the investigation was looking at "connections between the Baniyas massacre ... and the latest terror attack" in Turkey.
Rights groups say at least 62 civilians were killed this month in an assault on a Sunni district of Baniyas, a Mediterranean city in Syria, after at least 50 people were killed in the nearby village of al-Bayda.