Foreign Secretary William Hague has condemned the "disproportionate use of force" by the Egyptian security services as he issued a fresh appeal to all sides to end violence.
In a call with Egyptian foreign minister Nabil Fahmy, Mr Hague said Britain condemned all acts of violence, whether by the military or by some demonstrators protesting at the overthrow of former president of Mohammed Morsi.
He said that attacks on mosques and churches were "unacceptable" and called for places of worship to be protected.
His comments came after security forces stormed the al-Fath mosque in Cairo while Muslim Brotherhood supporters have been blamed for a series of attacks on Coptic Christian churches.
"The Foreign Secretary emphasised UK condemnation of all acts of violence, whether disproportionate use of force by the security forces or violent actions by some demonstrators," a Foreign Office spokesman said.
"They also discussed the recent attacks on places of worship and the Foreign Secretary stressed that attacks on mosques and churches were unacceptable and that places of worship must be protected."
Mr Hague urged the Egyptian government to return to the political road map published last month based on dialogue between parties who accepted peaceful political processes.
"He underlined the need for urgent steps by all sides to end the violence and enable a return to dialogue. The Foreign Secretary also emphasised the EU's collective determination to support a peaceful resolution of the situation," the spokesman said.