Supporters and opponents of ousted Egyptian President Mohamed Morsi clashed again Monday on the outskirts of Cairo's Tahrir Square.
Security officials said fighting broke out after a group of Morsi supporters passed near Tahrir during a protest march. The officials said security forces intervened.
Earlier Monday, Mr. Morsi's family spoke out against the country's military, threatening to use legal measures to gain the former leader's release.
At a news conference in Cairo, the former president's son, Osama Morsi, accused the Egyptian military of kidnapping his father. He said the family has not seen their father since July 3 when Egypt's military overthrew Mr. Morsi's democratically elected government.
"I sent a message to the international media, and civil society organizations and the United Nations to uphold the responsibility of the safety and security of the president, who is still the legitimate president. We are placing the responsibility of his safety upon everyone, and we don't exempt anyone from the responsibility. What happened is a complete crime of abduction and no less, and a perfect example of the kidnapping of the people's will and kidnapping an entire nation.''
Mr. Morsi's daughter, Shaimaa, also had harsh words for Abdel Fattah al-Sissi, the army commander and defense minister who played a central role in forcing Morsi from office.
"We hold responsible the leader of the bloody military coup and his group, the security and safety of the health of my father, the civilian and the president.''
Military officials say they have detained Mr. Morsi for his own protection and that he is in good health.
Mr. Morsi's Muslim Brotherhood has been holding near daily demonstrations in Cairo and across the country, demanding his release and reinstatement.
He had served only one year of his term as Egypt's first democratically elected president following the removal of longtime leader Hosni Mubarak in 2011.
Egypt's military-backed interim leaders are pressing ahead with their road map for returning the country to democratic rule.
On Sunday, a panel of experts charged with rewriting controversial parts of the suspended constitution met for the first time. Egypt's interim government has said it intends to hold new elections under a revised constitution early next year.