Update | Egypt's Mursi accused of deadly conspiracy with Hamas

Egypt's authorities yesterday formally detained Mohammed Mursi on suspicion of collaborating with Palestinian militants in murdering policemen and staging prison breaks, as tens of thousands of the deposed president's supporters and opponents staged rival rallies.

Mursi's detention, under a court order, for a renewable 15 days further ramped up tension as those applauding the decision and those angrily demanding the Islamist leader's reinstatement flooded various parts of Cairo.

The Arab world's most populous country has been convulsed by violence for the past three weeks, with some 200 people killed since Mursi's ousting by the army on July 3, many in clashes between his supporters and his opponents.

Clashes broke out in Cairo's Shubra neighbourhood in the early afternoon, leaving 10 people wounded as the two sides traded stones. Another 15 people were wounded in clashes in the Mediterranean city of Alexandria, the health ministry said. Police broke up the clashes with tear gas, state media reported.

But the overwhelming number of marches remained peaceful, with thousands of Mursi's supporters gathering in a north Cairo square before setting off through the streets.

At Cairo's Tahrir Square, tens of thousands of anti-Mursi supporters gathered in response to a call by the army chief General Abdelfattah Said El-Sisi on Egyptians to show their support for a security clampdown on "terrorism". The protesters waved Egyptian flags and held up posters of Sisi, who served as Mursi's defence minister before ousting him.