The United Nations human rights office voiced its regret over the loss of life in the violent clashes on Sunday in the Egyptian capital and called on authorities to carry out an impartial and independent investigation into the incident. At least 24 people are reported to have been killed and hundreds injured, the Office of the UN High Commissioner for Human Rights (OHCHR) said. "We call on the authorities to investigate and to ensure the impartiality and independence of the investigation," Rupert Colville, OHCHR''s spokesperson in Geneva, told reporters. "We express our regret over the loss of life as well as over those injured while attempting to exercise their rights to freedom of peaceful assembly and expression," UN news centre quoted Colville as saying. He recalled that the Egyptian revolution was achieved through "non-violence and responsible assembly and expression," and urged the authorities to ensure the protection of all, including minority groups, in their rightful exercise of such freedoms. In a statement issued by his spokesperson, UN Secretary-General Ban Ki-moon appealed to Egyptians to remain united and called on the country''s transitional authorities to guarantee the human rights and civil liberties of all citizens, regardless of their faith.