Turkey believes fighters loyal to Syrian President Bashar al-Assad were behind two car bombings that killed 46 people in a Turkish border town where thousands of Syrian refugees live, officials said on Sunday.

Authorities have arrested nine people, all Turkish citizens, including the alleged mastermind, after the bombings in Reyhanli on Saturday, Deputy Prime Minister Besir Atalay told reporters.

Foreign Minister Ahmet Davutoglu said those involved were also thought to have staged an attack on the Syrian coastal town of Banias a week ago in which at least 62 people were killed.

The car bombs increased fears that Syria's civil war was dragging into neighboring states despite renewed diplomatic moves toward ending two years of fighting in which more than 70,000 people have been killed.

"The attack has nothing to do with the Syrian refugees in Turkey, it's got everything to do with the Syrian regime," Davutoglu said in an interview on TRT television.

"We should be careful of ethnic provocations in Turkey and Lebanon after the Banias massacre," he said.

The conflict has inflamed a confrontation between Sunni and Shiite Muslims in the Middle East, with Shiite Iran supporting Assad, and Sunni powers such as Saudi Arabia backing the rebels. Banias is a Sunni pocket in the middle of a large Alawite enclave on Syria's Mediterranean coast. Activists in the area accuse militias loyal to Assad, an Alawite, of ethnic attacks.

Backlash fears

Reyhanli has become a logistical base for the rebels fighting Assad just over the border, and the thousands of Syrian refugees there are mostly Sunni.

Interior Minister Muammer Guler said the attacks had been carried out by a group known to the Turkish authorities and with direct links to Syria's Mukhabarat intelligence agency.

The bombs ripped into crowded streets near Reyhanli's shopping district in the early afternoon on Saturday, scattering concrete blocks and smashing cars as far as three blocks away. Among the dead were 35 Turks and three Syrians, Atalay said.

Syrian Information Minister Omran Zubi, speaking on Syrian state TV, accused Turkey of responsibility for the bloodshed in Syria by aiding al-Qaida-led rebels.

The bombings marked the biggest incident of cross-border violence since the start of Syria's civil war and have raised fears of Turkey being pulled deeper into the conflict. Harsh accusations from both sides signaled a sharp escalation of already high tensions between the two former allies.

The bombings occurred as prospects improved this week for diplomacy to try to end the war after Moscow and Washington announced a joint effort to bring the government and rebels to an international conference.

They also highlight the strain the war and the refugee exodus are placing on neighboring states, with local people resentful over stretched economic resources and the risk of violence. Turkey is housing more than 300,000 refugees.

Reuters-AP