Earlier in that day, Celik plead guilty for the murder of Russian pilot Oleg Peshkov whose Su-24 was shot down by the Turkish Air Force last November, according to Turkish Dogan News Agency.
Celik has been arrested on charges of illegal arms possession, which were denied by the detainee, CNN Turk reported.
"If Russia demands Celik's extradition, Turkey is likely to refuse… Moreover, in December last year, Russia withdrew from its treaty with Turkey on mutual legal assistance in civil, commercial and criminal cases, though this did not stipulate Turkey or Russia extraditing their citizens," the source told RIA Novosti.
Although Celik said he killed Peshkov, he refused to give further information regarding the incident, the source said. The man also added that he doesn't regret killing the Russian pilot and given an opportunity he'd do the same thing again.
Earlier it was reported that Celik was arrested in the Turkish city of Izmir upon his arrival from Syria, where he was fighting against the country's government forces alongside Turkmen militants.
Interestingly, Celik and his friends were arrested not due to their suspected involvement in the killing of the Russian pilot or fighting in Syria, but because they showed up to a restaurant in Izmir with their guns. Understandably, people got scared and someone called the police who arrived and seized a Kalashnikov assault rifle and two pistols during the arrest.
The Russian Su-24 bomber was shot down by a Turkish F-16 fighter jet over Syria on November 24, 2015 and fell four kilometers (2.5 miles) from the Turkish border. The crew of the plane ejected and one of its pilots, Peshkov, was killed by fire from the ground, while the second pilot survived and was later rescued.