Ousted Egyptian president Mohamed Morsi has been detained over alleged contacts with Hamas to help in his escape from prison in 2011, the country's official news agency reported today.

Mr Morsi has been detained for 15 days for investigation into the charges.

Egypt's military has been holding him in an undisclosed location since deposing him on July 3.

Mr Morsi's detention can be extended as the inquiry continues. It is believed he has already been interrogated.

The announcement comes after military strongman General Abdel-Fatah el-Sissi called for mass demonstrations today to oppose what he called "terrorism" - a clear reference to Mr Morsi's Muslim Brotherhood.

The Brotherhood's spiritual leader responded by calling Gen el-Sissi a "traitor" and charging that the coup led by him was worse than destroying the Kaaba in Mecca, the holiest site in Islam.

The Brotherhood also called for mass protests today, escalating fears of clashes between the two opposing groups of demonstrators or with the military, which has pledged to keep order and prevent violence.

The case concerns the mass jailbreak of dozens of Muslim Brotherhood leaders during the popular uprising in 2011 that toppled Mr Morsi's predecessor, President Hosni Mubarak. There have been many reports in Egyptian media that the Brotherhood collaborated with Hamas, its Palestinian wing, and Hezbollah militants in Lebanon to arrange the breakout.

Muslim Brotherhood officials have said they were aided by local residents in breaking out of prison, not foreigners.

It was reported that Mr Morsi is being investigated over allegations of collaborating with Hamas "to carry out anti-state acts, attacking police stations, army officers and storming prisons, setting fire to one prison and enabling inmates to flee, including himself, as well as premeditated killing of officers , soldiers and prisoners".