Egyptian police arrested more than 500 supporters of the blacklisted Muslim Brotherhood when deadly violence erupted on the anniversary of the 2011 uprising, the interior minister said Monday.

Protesters and security forces clashed Sunday after Islamists called for demonstrations against President Abdel Fattah al-Sisi's government as Egypt marked the fourth anniversary of the toppling of ex-strongman Hosni Mubarak.

The Islamic State group's Egyptian affiliate, Ansar Beit al-Maqdis, claimed in a video released Monday the killing of a police officer whose body was found almost two weeks ago.

Egyptian troops found the body of Ayman al-Desouky, who had been kidnapped from near the town of Rafah on the border with the Gaza Strip, during a search operation in North Sinai on January 13.

The Islamic State (IS) group, which has sown a trail of terror across Syria and Iraq, is neither a state nor justified by Islam, Egypt's top Muslim cleric said Monday.

"We have already asserted that we should never use the term Islamic State for ISIS," Egypt's Grand Mufti Sheikh Shawky Allam said at a public forum in Singapore.

An Egyptian appeals court on Monday sentenced a doctor to more than two years in jail for performing a female circumcision that killed a teenage girl, overturning an acquittal.

A lower court in November had acquitted the doctor and the father of 14-year-old Sohair al-Bataa in the first such case brought to the courts since the procedure was banned in 2008.

Human Rights Watch on Monday accused Egyptian police of using "excessive force" against protesters after 20 people were killed in clashes on the fourth anniversary of its 2011 uprising.

The clashes between protesters and security forces in Cairo and the coastal city of Alexandria on Sunday came after Islamists called for demonstrations against President Abdel Fattah al-Sisi's government.

Ousted Egyptian president Hosni Mubarak's two sons have been released from prison pending a retrial, the interior minister said Monday, four years after their arrest following an uprising that toppled their father.

Alaa and Gamal Mubarak -- symbols of corruption during their father's three-decade rule -- were ordered free by a court ahead of the January 25 anniversary of the 2011 revolt that overthrew the longtime leader.

Egypt on Sunday extended by three months a state of emergency in force since late October in areas of North Sinai after an attack that killed 30 soldiers.

The authorities are battling a dogged insurgency in North Sinai, where jihadists have carried out regular attacks on security forces since the army ousted Islamist president Mohamed Morsi in July 2013.

Egyptian security officials on Sunday said the release of Alaa and Gamal Mubarak pending a corruption retrial had been delayed, after state media reported they had walked free from prison.

A court had ordered the release of the two sons of the ousted strongman Hosni Mubarak last week, ahead of the January 25 anniversary of the 2011 uprising that overthrew him.

Clashes between protesters and security forces left at least 14 people dead on Sunday, the anniversary of Egypt's 2011 revolt that toppled strongman Hosni Mubarak.

Authorities had tightened security in Cairo and other cities after Islamists called for protests against the government of President Abdel Fattah al-Sisi, the former army chief who ousted his Islamist predecessor Mohamed Morsi in 2013.

Syria's opposition factions called Saturday for "radical democratic change" in the war-torn country ahead of April talks aimed at unifying their plan for a political solution to the conflict.

In a two-day conference held in Cairo, the regime-tolerated opposition met with members of the exiled National Coalition and agreed on a 10-point vision, as well as announcing fresh talks slated for April.