William Hague has expressed deep concern at the ongoing violence in Egypt, urging authorities and opposition activists to show restraint as protests against president Mohamed Morsi raged.
Rocks, firebombs and sticks were used as weapons in fighting between supporters and opponents outside the presidential palace in Cairo.
Thousands of upporters of the Muslim Brotherhood, the Islamist party, have flocked to the palace, responding to a call for them to demonstrate their solidarity.
Three presidential advisers have quit over Morsi's handling of the constitutional crisis, which began when he issued a declaration purporting to protect the assembly drafting the new Egyptian constitution from interference from judges. But in effect, the declaration makes him immune from any legal challenge
The health ministry said 211 people had been injured so far.
Foreign Secretary Hague said: "I am concerned by reports of violent clashes following earlier peaceful protests in Cairo. I urge all sides to show restraint.
"The UK remains committed to supporting Egypt's political transition and strengthening democracy.
"We are in close contact with both the Egyptian authorities and leaders of the opposition.
"We call on the Egyptian authorities to make progress on transition in an inclusive manner which allows for a constructive exchange of views.
"We urge all parties to resolve their differences through a process of dialogue which allows all voices to be heard."
According to Reuters, riot police have been deployed to try to contain the violence.
Vice President Mahmoud Mekky has attempted to offer a compromise over the controversial draft constitution which sparked the uprising, and offered that a written agreement between the two sides could be submitted to the next parliament, to be elected after a referendum on the constitution on Dec. 15.
Mursi had returned to his home after being forced to flee earlier this week as protesters surrounded the building.
Mohamed ElBaradei, the de-facto leader of the Egyptian opposition, tweeted as the violence raged:
According to a Reuters report, Morsi's supporters tore down tents erected by around 300 opposition activists, who had attempted to "occupy" the space with a tent city. They came armed with pellet guns.
The pro-Morsi group chanted "The people want to cleanse the square" and "Morsi has legitimacy", AFP reported.
US Secretary of State Hillary Clinton said at a news conference in Brussels: "It needs to be a two-way dialogue ... among Egyptians themselves about the constitutional process and the substance of the constitution."