Relations between once close allies Iran and Turkey are rapidly deteriorating over Ankara's strong support for Syrian rebels fighting against Iran's key ally, Syrian President Bashar al-Assad. In an unprecedented move, Tehran suspended visa-free travel with Turkey for the first time in nearly 50 years.



Iran observer Mehrdad Emadi, who works for the international affairs consultant firm "Betamax," said the suspension of visa-free travel is significant.

"It is quite actually meaningful in the context of the rising tensions between the two countries," said Emadi. "And, I think there are too many sources behind this growing tension - one is the conflicting positions in the management of the Syrian crisis. We have never had such a thorny relationship between the two countries."

Turkish Prime Minister Recep Tayyip Erdogan this week accused Tehran of being ungrateful for his government's efforts to defuse international tensions over Iran's controversial nuclear program. Two years ago, Turkey - as a temporary member of the U.N. Security Council - voted against Iran sanctions.

Former senior Turkish diplomat Murat Bilhan said it is difficult to read Iran.