Turkey has arrested one of the major suspects in the twin car bombings that killed at least 51 people in a city near the Syrian border, the city's governor said on Friday.
"We captured one of the chief actors involved in the incident at 11:40 pm last night," said Celalettin Lekesiz, governor of southeastern Turkey's Hatay city where the bombs went off.
"There are still two other major suspects at large," he added in televised remarks.
The man, who allegedly purchased the vehicles used in the bombings, was caught trying to cross the border into Syria along with his two accomplices.
"Our security forces are tracking them too," said Huseyin Celik, deputy chairperson of the ruling Justice and Development Party (AKP). "I am sure they will be caught as soon as possible and brought to justice."
Three others were also arrested after a court evaluation on Friday, pushing the total number of arrests to seven.
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In a parallel development, the police chief of Reyhanli border town was sacked amid an investigation into whether there was a failure on part of the security forces to prevent the deadly incident.
Last Saturday's attacks were the deadliest case of what observers see as an increasing regionalisation of the Syrian conflict that started in March 2011, and came as key brokers Washington and Moscow made an unprecedented joint push for peace talks.
Ankara has blamed the Syrian regime for the bombings and said on Sunday that Damascus had crossed a "red line" and it reserved the right to "take any kind of measure" in response.
All suspects are Turkish nationals believed to be backed by the Syrian government, but Damascus has denied involvement and has offered to carry out a joint investigation.
Turkish Prime Minister Recep Tayyip Erdogan rejected the offer and said his government would have a "road map" on the Syrian crisis after discussing the incident with Washington and other allies in the region.
Erdogan met US President Barack Obama on Thursday and the two leaders reiterated their calls for Syrian President Bashar al-Assad to step down and for an end to the killing which rights activists say has claimed some 94,000 lives.