At least 34 people have been killed and dozens hurt in Egypt in clashes between police and supporters of the deposed Islamist President Mohammed Morsi.
More than 200 members of the Muslim Brotherhood were arrested in Cairo, where 26 of the deaths were reported.
Supporters or Morsi marched in several cities, as the military-backed government marked the 40th anniversary of the 1973 Arab-Israeli war.
Morsi supporters say he was deposed in a military coup in July.
Hundreds of people had gathered in Cairo’s Tahrir Square to celebrate the anniversary.
Jets and Apache helicopters flew overhead in formation, as part of a grand display of military hardware by the government.
The crowd cheered the flypasts, a number of people carrying portraits of defence chief Gen Abdel Fattah al-Sisi. Some want him to stand as Egypt’s next president.
But the BBC’s Quentin Sommerville in Cairo says supporters of Mr Morsi also took to the streets in their thousands, trying to make their way to the square and calling Gen Sisi a murderer. Security forces used tear gas and fired into the air to stop them.
Supporters and opponents of Egypt’s ousted Islamist President Mohammed Morsi clash in Cairo The rival protests in Cairo turned into running street battles
Supporters of ousted President Mohammed Morsi are detained during clashes with riot police in Cairo More than 200 members of the Muslim
Brotherhood have been arrested in connection with the violence, an Egyptian security source told BBC Arabic.
Egyptians, one holding a poster of General Abdel Fattah al-Sisi, pose with soldiers as they gather on Tahrir Square to mark the 40th anniversary of the 1973 Arab-Israeli war Supporters of the military have been converging on Tahrir Square to mark the 40th anniversary of the 1973 Arab-Israeli war
President Mansour lays a wreath as part of events to mark the start of the 1973 war with Israel President Mansour laid a wreath as part of planned commemorations
A man carries a poster of ousted Egyptian President Mohammed Morsi, calling for his trial as people gather to mark the 40th anniversary of the Arab-Israeli war Egyptian society remains polarised by the military overthrow of Islamist president Mohammed Morsi in July.
In the upscale Dokki district, a number of protesters were hit by live rounds, some by birdshot. In return they threw rocks at police and soldiers, our correspondent says.
The street battles raged for hours, with small fires burning and black smoke rising in several parts of the capital.
But the military succeeded in keeping the rival supporters apart, our correspondent says.
The interior ministry earlier warned it would confront any “attempts that may disturb the 6 October celebrations”, the Mena state news agency reported.
In a televised address, Prime Minister Hazem Beblawi described it as a “critical time” for the country and urged Egyptians to “stand together, be optimistic about the future”.
The health ministry said that in addition to the Cairo deaths, one person was killed in Delga, about 300km (190 miles) south of Cairo, and another in Bani Suef, 80km south of the capital.
There were also clashes in the Suez Canal city of Ismailiya.
Hundreds of Islamist protesters have died in violence since the Egyptian military deposed Mr Morsi in July, 13 months after he was elected as president.
He and other senior Brotherhood figures have been imprisoned and face trial.
The authorities are moving to seize the movement’s assets after its activities were banned as part of a crackdown.
However, Brotherhood supporters have continued to take to the streets to protest – albeit in smaller numbers than before.