Turkey will investigate the deportation of an Egyptian facing execution in Cairo over a car bomb and has suspended eight policemen involved, the Istanbul governor's office said on Wednesday.
Mohamed Abdelhafiz Ahmed Hussein, whom the Muslim Brotherhood movement identifies as a member, was among 28 people sentenced in absentia to death in July 2017 for killing Egypt's public prosecutor in the attack, according to state media.
He was sent back to Egypt last month from Istanbul's main Ataturk airport on arrival from Somalia for not having a visa.
The case adds to strained Turkey-Egypt relations since the army ousted President Mohamed Morsi, of the Brotherhood, following mass protests against his rule in 2013.
The Istanbul governor's office said on Tuesday that when Hussein arrived, there was no information he was facing trial anywhere, and he did not request protection, so officials deemed him an "unacceptable passenger" due to lack of a Turkish visa.
In a separate statement on Wednesday, the governor's office said a commission had been set up to investigate the deportation and eight police officers were suspended from duty over it.
An adviser to Turkish President Tayyip Erdogan said it was wrong to repatriate anyone facing charges in Egypt and the matter needed checking.
"During the leadership of (Egyptian President Abdel Fattah) Sisi, Turkey has not and does not hand over anyone facing the death penalty or any other charges," Yasin Aktay wrote in the pro-government Yeni Safak newspaper on Wednesday.
The Muslim Brotherhood has close ties with Turkey's ruling AK Party and many of its members have fled to Turkey since the group's activities were banned in Egypt.
Cairo considers the Brotherhood, the world's oldest Islamist movement, a terrorist organisation. Most of its senior members have been arrested, driven into exile or underground.
Defendants sentenced in absentia in Egypt are automatically retried once they are captured or turn themselves in.
Sources in Egypt's National Security Service said Hussein was questioned and moved to jail ahead of his retrial after arriving in Egypt.