Thousands of protesters have ignored a curfew in Egypt's chaos-stricken capital as widespread demonstrations demanding reforms and an end to President Hosni Mubarak's three-decade rule continue.
The defiant stand came as David Cameron personally spoke to the embattled leader to express his "grave concern" about violence against the anti-government dissidents, who are entering their sixth day of action.
The Prime Minister urged Mr Mubarak to "take bold steps to accelerate political reform and build democratic legitimacy" rather than attempt to repress dissent, according to Downing Street.
In a joint statement with French President Nicolas Sarkozy and German Chancellor Angela Merkel, Mr Cameron said: "The Egyptian people have legitimate grievances and a longing for a just and better future.
"We urge President Mubarak to embark on a process of transformation which should be reflected in a broad-based government and in free and fair elections."
Mr Cameron's intervention came in a telephone call last night, as tens of thousands of protesters remained on the streets.
In Cairo, swathes of citizens ignored a 4pm to 8am curfew and roamed the city under the watchful glare of the army, which has increased its presence of tanks and armoured personnel carriers.
Residents have reported gangs of youths, some on motorbikes, looting supermarkets, shops, shopping centres and homes. Gunfire was also heard in Cairo's centre as well as outlying districts.
More than 50 people are said to have died during five days of clashes with police, and thousands more have been injured.
Mr Mubarak tried to ease the crisis last week by sacking his cabinet and appointing a moderate new deputy.
But the UK and US - previously strong allies of the regime - have failed to give their backing. America has suggested it could withdraw Egypt's multibillion-dollar aid package if civil liberties are not respected.