Britain has called for "maximum restraint" and strongly condemned violence in Egypt after two days of clashes left 38 people dead.
Rioting broke out in the city of Port Said after 21 people were sentenced to death for their part in violence at a football game in which 74 people died last year.
At least 27 people were reported killed and hundreds injured in the backlash while another 11 died across the country in confrontations with police and protesters marking Friday's second anniversary of the uprising that ousted president Hosni Mubarak.
Foreign Office Minister Alistair Burt said such violence "can have no place in a truly democratic Egypt".
"I am deeply concerned by reports of violent clashes resulting in a number of deaths and injuries, following demonstrations to mark the second anniversary of the 25 January revolution and the verdict in the Port Said court case today," he said.
"This cannot help the process of dialogue which we encourage as vital for Egypt today, and we must condemn the violence in the strongest terms.
"We call on all parties to exercise maximum restraint and to ensure that all protests remain peaceful. I offer the condolences of the UK to the families of all the victims."
The UK remained "committed as a strong friend of Egypt and the Egyptian people to support the aim of strengthening true democracy", he added.
"The right to peaceful freedom of expression and assembly is an essential part of this, but the violence we have seen today can have no place in a truly democratic Egypt."
Two footballers were reported to be among the dead in Port Said where angry protesters tried to storm a prison to free some of the defendants in the football violence trial. The military has been called in to restore security.