Iran's foreign minister is set to visit Turkey on Saturday in the midst of a high-level corruption probe looking into illicit money transfers to Tehran.
Mohammad Javad Zarif's trip comes as Turkey seeks to improve economic and political ties with its neighbour but with the government in Ankara embroiled in a deep political crisis over the corruption scandal.
Dozens of people were arrested last month, including allies of Prime Minister Recep Tayyip Erdogan, accused of bribery over construction projects and allegations of gold smuggling to Iran aimed at dodging international sanctions.
Iranian officials on Monday arrested Babak Zanjani, a tycoon is believed to have played a major role in busting sanctions imposed on Tehran over its disputed nuclear programme.
Zanjani was involved in illegal gold sales from Turkey to Iran that sparked the graft investigation, according to media reports.
Turkey's state-owned Halkbank has come under the spotlight in the sweeping investigation, accused of being involved in the illegal gold sales to Iran in return for energy imports.
Halkbank chief executive Suleyman Aslan was arrested and charged with taking bribes after police reportedly found $4.5 million stashed in shoeboxes in his home.
But the bank denied any wrongdoing and said it stopped transactions to Iran as of June last year after the United States announced further sanctions against the Islamic republic.
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The government has defended the bank, with Erdogan claiming that it was being targeted by unnamed international plotters.
"This bank is intimidating Turkey's enemies," said the Turkish premier last month.
Deputy Prime Minister Ali Babacan said Tuesday that Halkbank was the only bank which could do business with Iran and that it gained the trust of Tehran and Washington.
Iran's ailing economy has been struggling in recent years under an array of international sanctions designed to coerce it into to reining in its controversial nuclear ambitions.
Turkey, which has very few resources of its own, is dependent on gas and oil imports from the neighbouring country.
Turkey and Iran are keen on mending fences after the June election of Iranian President Hassan Rouhani, which has seen renewed talks with world powers on its contested nuclear programme.
Turkish Foreign Minister Ahmet Davutoglu visited Tehran in November.
But Ankara and Tehran disagree on the civil war in neighbouring Syria.
Iran is a key ally of Syrian President Bashar al-Assad's embattled regime, while Turkey is a strong backer the rebels seeking to overthrow him.