Prime Minister David Cameron has condemned "despicable" scenes of violence in the Egyptian capital Cairo, where supporters of Hosni Mubarak have attacked demonstrators calling for the president's removal.
Speaking alongside United Nations Secretary-General Ban Ki-Moon after talks in 10 Downing Street, Mr Cameron said that the political transition to a new broad-based government in Egypt needed "to be accelerated and to happen quickly".
Central Cairo has witnessed the worst scenes of violence since anti-Mubarak demonstrations began more than a week ago, with several thousand supporters of the president, some riding horses and camels and wielding whips, attacking protesters in Tahrir Square.
Officials say a member of the security forces has been killed and more than 600 people wounded in pitched battles in and around Cairo's Tahrir Square.
Speaking outside Number 10, Mr Cameron said: "If it turns out that the regime in any way has been sponsoring or tolerating this violence, that would be completely and utterly unacceptable.
"These are despicable scenes we are seeing and they should not be repeated."
Mr Ban added: "I once again urge restraint to all sides... Any attack against peaceful demonstrators is unacceptable and I very strongly condemn it."