Britain will work with Egypt's interim authorities despite not supporting the military intervention that toppled Islamist president Mohammed Morsi, Foreign Secretary William Hague said on Thursday.

Hague insisted that Britain had to be "practical" in dealing with the situation after the Egyptian army forced Morsi out of office and held him in detention after days of deadly protests against his rule.

Egypt's largely state-run press on Thursday unanimously hailed the army's overthrow of Islamist President Mohammed Morsi as a "legitimate" revolution.

"The people's legitimacy was victorious," the flagship government-owned Al-Gomhuriya splashed on its front page.

Egypt's army is "preventively" holding President Mohammed Morsi after his ouster by an army decree, a senior army official told Agence France Presse Thursday.

"He is being held preventively for final preparations," the official said, suggesting Morsi might face formal charges over accusations made by his opponents.

U.N. leader Ban Ki-moon believes Egyptians have "legitimate concerns," but is worried about the military's ousting of President Mohammed Morsi, a spokesman said Wednesday.

"Egyptians in their protests have voiced deep frustrations and legitimate concerns. At the same time, military interference in the affairs of any state is of concern," said deputy U.N. spokesman Eduardo del Buey.

U.S. President Barack Obama on Wednesday called for a swift return to elected civilian rule in Egypt, saying the United States was "deeply concerned" by the military's toppling of Mohammed Morsi.

Obama also sent a signal to military leaders, ordering a review of the hundreds of millions of dollars in annual U.S. aid to Egypt in light of the army's move against Morsi, the nation's first democratically elected president.

Consultations start "now" for a new Egyptian government after the military deposed president Mohamed Morsi, opposition leader Amr Moussa told Agence France Presse.

"Consultations will start from now, for a government and reconciliation," said the former Arab League chief, who ran unsuccessfully against Morsi for the presidency last year.

Egyptian security forces on Wednesday arrested two senior leaders of the Muslim Brotherhood close to ousted president Mohamed Morsi, security officials said.

Saad al-Katatni, who heads the Freedom and Justice Party -- the political arm of the Muslim Brotherhood -- and Rashad Bayoumi, the deputy head of the Islamist movement were detained, the officials said.

Saudi King Abdullah on Wednesday sent a message of congratulations to Egypt's new caretaker president, saying his appointment comes at a "critical" time in the nation's history, the official Saudi news agency SPA reported.

"On behalf of the people of Saudi Arabia I congratulate you for taking over the leadership of Egypt at this critical time in its history," Abdullah said in the first message of congratulations by an Arab leader to Adly Mansour.

The United States on Wednesday ordered the mandatory evacuation of its embassy in Cairo, just hours after the Egyptian military ousted president Mohamed Morsi.

Asked if reports of the evacuation were true, a U.S. official told Agence France Presse "yes."

Four supporters of ousted Egyptian president Mohamed Morsi were killed on Wednesday in clashes with the army and police in the western city of Marsa Matruh, a security official told Agence France Presse.

Another 10 people were injured after the group of armed supporters stormed the city's security headquarters, the official said.