The suspect, identified by authorities only as Ziya T., had been on the run since the body of Sarai Sierra, a 33-year-old mother of two boys, was discovered last month. Authorities said Sierra died of a fatal blow to the head.
She had traveled to Turkey to explore her photography hobby. She did so alone after a friend who was supposed to join her canceled for financial reasons. Sierra's body was found hidden near Istanbul's ancient city walls on Feb. 2, 12 days after her family reported her missing.
Interior Minister Muammer Guler said the suspect was detained in the province of Hatay, near the border with Syria, as he entered Turkey. "We had information that the suspect had escaped abroad. He was believed to be in Syria," Guler told reporters. "He was detained today in Hatay, as he was entering Turkey and was handed over to court officials."
Guler did not provide any other details about the arrest.
Turkish news reports have described the man as a homeless scrap paper collector who used to hang around the city walls. The man was expected to be taken to Istanbul for questioning and to face possible formal arrest and charges.
Television footage showed the man, wearing military camouflage pants and a navy zipped jacket, being escorted down some stairs into a police armored personnel carrier.
Turkish news reports have said police identified Ziya T. as the main suspect in the case after DNA samples taken from his two brothers and a sister matched those found beneath Sierra's nails. Police would not confirm these reports, saying the investigation is ongoing.
Guler said police identified the suspect after inspecting thousands of security camera videos and conducting a "series of tests."
In the United States, Sierra's family was following the latest developments in the case, said her sister, Christina Jimenez, but she declined to comment at this crucial stage in the investigation. "We don't want to say the wrong thing," Jimenez said.