Erdoğan says Egypt's Morsi didn't die of natural causes

Turkish President Recep Tayyip Erdoğan on Tuesday said he does not believe the death of Egypt's president was natural, state-run Anadolu Agency reported.

Egypt's former president Mohammed Morsi, a top figure in the now-banned Islamist movement Muslim Brotherhood, died on Monday after collapsing during a Cairo court session.

"I don’t believe this is a normal death," Anadolu quoted Erdoğan as saying over the demise of Egypt's ousted president following a funeral prayer in absentia he attended for Morsi in Istanbul.

The former Egyptian president died from a heart attack Monday during a court session, according to country's state television.

Thousands joined in a prayer called by Turkey's Religious Affairs Directorate (Diyanet) at Istanbul's Fatih Mosque, one of the many held across the country, according to Anadolu.

"I would like to pay homage and extend my condolences to all of the people of Egypt," said Erdoğan following the prayer and called Morsi Egypt's rightful leader and a "martyr."

Relations between Turkey and Egypt have been practically non-existent since the Egyptian military, then led by Abdel Fattah al-Sisi, in 2013 ousted democratically-elected president Morsi. Sisi has since become president.

Erdoğan, who had forged close ties with Morsi, has strongly denounced his ouster and called for the release of Muslim Brotherhood prisoners in Egypt.

The Islamic Brotherhood leader was elected president in 2012 but was ousted in a military coup a year later. The military crushed the Muslim Brotherhood movement in a major crackdown, arresting Morsi and many others of the group's leaders, who have been in prison undergoing multiple trials ever since the coup.

Rights group Amnesty International has called for a fair and transparent investigation into Morsi's death and raised questions about his treatment in prison.

The former president, who had health problems including diabetes and kidney disease, was held in solitary confinement for much of his incarceration and denied adequate medical care, according to Human Rights Watch. 

United Nations also has called for an independent investigation into the death of former Egyptian president, BBC said.