Egypt has opened an investigation into deposed president Mohamed Morsi for allegedly handing over to Qatar "documents relevant to national security," state news agency MENA reported on Wednesday.
Morsi is already facing the death penalty in several trials and his supporters have been the target of a bloody crackdown by the authorities that has left more than 1,400 dead since he was turfed out in July 2013.
The former leader is suspected of providing "documents relevant to national security to Qatar via the Qatari Al-Jazeera chain when he was president of the republic (...), damaging the country's national security", said MENA.
In March Egypt's interior minister accused Morsi's secretary Amin El-Serafi of having delivered documents regarding the army, its armaments and the deployment of its troops to a chief editor of Al-Jazeera and member of the Islamist president's Muslim Brotherhood.
The movement was listed as a terrorist group after Morsi's overthrow on July 3, 2013.
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Relations between Egypt and Qatar soured after Morsi's ouster, as Cairo criticised the rich emirate's backing for the Muslim Brotherhood and Doha slammed Egypt's crackdown on Morsi supporters.
Egypt condemned three English-language Al-Jazeera journalists to prison sentences of between seven and 10 years in June for aiding the blacklisted Muslim Brotherhood and spreading false news that portrayed Egypt as being in a state of "civil war".
Less than a year after former armed forces chief Abdel Fattah al-Sisi deposed Egypt's first freely elected president, Sisi won presidential elections in May, partly thanks to his image as a strongman who can restore stability to a country in tumult since an uprising toppled autocrat Hosni Mubarak in 2011.
But his government is regularly accused of using the courts to crack down on Morsi supporters, with the former president and practically all Muslim Brotherhood leaders finding themselves behind bars, risking the death penalty.
More than 15,000 pro-Morsi demonstrators have also been jailed, while hundreds have been sentenced to death in mass trials that caused international outrage.
Morsi has been charged in three cases including a trial for spying that involves Gaza's Hamas movement and Iran.