UN leader Ban Ki-moon on Thursday called on the Egyptian military to free overthrown president Mohammed Morsi and Muslim Brotherhood leaders, a spokesman said.

Ban demanded that Morsi and his high-level backers "be released or have their cases reviewed transparently without delay," said deputy UN spokesman Eduardo del Buey.

Morsi and several Muslim Brotherhood leaders have been detained since the military drove him from power on July 3 in response to massive protests calling for his ouster.

With tensions again rising in Egypt ahead of rival rallies by followers of Morsi and the army on Friday, the spokesman said Ban "is following closely, and with growing concern, developments in Egypt.

"The secretary general once again urges all sides to act with maximum restraint. He supports the rights of all Egyptians to hold peaceful protests.

"He calls on the interim authorities to ensure law and order along with guaranteeing the safety and security of all Egyptians."

Ban "renews his calls for a meaningful national dialogue and an inclusive reconciliation process. The aim must be to chart a peaceful path towards a full return of civilian control, constitutional order, and democratic governance," said del Buey. (AFP)