Turkey's Ministry of Foreign Affairs on Saturday advised Turkish nationals to postpone all non-urgent travel to Russia, the latest move in an escalating row between Moscow and Ankara over a Russian jet downed by Turkey on Tuesday.NATO member Turkey's foreign ministry said in a statement that following difficulties faced by Turkish visitors and residents in Russia, it advised Turks to postpone all non-urgent travel.The statement said that Turkish nationals in Russia can reach the embassy in Moscow through "007 495 994 48 08" and "007 926 732 82 38" phone numbers and "embassy.moscow@mfa.gov.tr" e-mail address. It added that the "0090 312 292 29 29" hotline of the ministry can be reached 7/24 to receive information.At least 26 Turkish businessmen were taken into police custody in Russia's Black Sea city of Krasnodar late Wednesday, according to Turkish diplomatic sources.Five of the group returned to Turkey on Saturday morning, Anadolu Agency reported.The Turkish embassy in Moscow has issued an advisory to its citizens in Russia, requesting them to carry their passports and ensure their visas and permits are valid. The embassy also reiterated that they should "meticulously obey the rules in Russia and warnings from the Russian authorities."However, Russia has recommended its citizens in Turkey return home. Russia's Ministry of Foreign Affairs said late on Thursday that it wanted its citizens not to travel to Turkey because of a perceived "terror threat". "We recommend our citizens residing in Turkey for special reasons to return to Russia," the ministry said in a statement.Russia also decided on Friday to unilaterally suspend its visa exemption for Turkish citizens starting from Jan. 1, 2016, with Russian Foreign Minister Sergey Lavrov saying the suspension was "for the sake of security of Russia and its citizens."Two Turkish F-16 fighter jets on an aerial patrol intercepted an unidentified warplane on Tuesday within engagement rules when it intruded into Turkish airspace on the Syria border.The intruding aircraft was warned about the violation 10 times within five minutes before it was shot down.The Russian Defense Ministry later announced that one of its SU-24s had been shot down. It crashed in the Syrian region of Bayirbucak, close to Yayladagi district of Turkey's southern Hatay province.NATO confirmed the accuracy of the information shared by Turkey about the violation.It was not the first time Russian fighter jets had violated Turkish airspace. In early October, Russian warplanes breached Turkish airspace. Russian officials apologized and pledged that no such incident would be repeated. Turkey had also renewed its warning on engagement rules, including a military response against violations of Turkish airspace.