A senior police officer was gravely wounded in an overnight bombing in Libya's restive second city of Benghazi, a security official told Agence France Presse on Saturday.

"Colonel Faouzi al-Oujli was critically injured when an explosive device placed in his car went off," said the eastern city's security spokesman, Colonel Mohamed al-Hijazi.

Rights group Amnesty International on Friday called for an immediate investigation into allegations that supporters of ousted Egyptian president Mohammed Morsi tortured opponents in Cairo.

"Evidence, including testimonies from survivors, indicates that supporters of deposed President Mohammed Morsi tortured individuals from a rival political camp," the group said in a statement.

US Middle East envoy William Burns arrived in Cairo on Friday night, a senior Egyptian official said, as international efforts to resolve Egypt's political crisis ramp up.

Burns, the under secretary of state for the Middle East, has already visited Egypt once since the July 3 ouster of president Mohammed Morsi.

Britain's embassy in the Yemeni capital Sanaa will be shut this weekend, the Foreign Office said, after the United States announced the temporary closure of two dozen embassies over fears of an al-Qaida attack.

Several British embassy staff have been withdrawn from Sanaa over the security fears, a spokesman for the Foreign Office in London said.

Egypt's interim vice president Mohammed ElBaradei has called for a halt to violence followed by talks with the Muslim Brotherhood and other backers of ousted president Mohammed Morsi.

His comments, in an interview with the Washington Post, were published Friday as Morsi supporters staged fresh rallies in Egypt in defiance of government orders that their protest camps be broken up.

Syrian opposition leaders said Friday that U.N. inspectors would have "unfettered" access to areas under rebel control to investigate the use of chemical weapons.

The Syrian National Coalition said in a statement it wanted the inspectors to go first to the town of Khan al-Assal, where an attack with chemical weapons was reported on March 19.

An explosive device detonated outside a police station in Libya's Benghazi on Friday, wounding five people, a security official told Agence France Presse, in the latest attack to hit the eastern city.

In recent months, Benghazi has been hit by a wave of bombings and assassinations targeting judges, the military and police officers.

A rights watchdog expressed fears Friday that an Italian Jesuit priest who went to meet with jihadists in northern Syria has been taken prisoner, calling for his immediate release.

The Syrian Observatory for Human Rights' call for Father Paolo Dall'Oglio's release comes three days after he went to meet with commanders of the Islamic State of Iraq and the Levant (ISIS).

U.S. Secretary of State John Kerry and his counterpart from the United Arab Emirates called on Friday for Egypt to return to normal and restore stability after fresh protests.

"Egypt needs to get back to a new normal," Kerry said on a stopover in London, after Islamist backers of Egypt's deposed president Mohammed Morsi staged defiant rallies.

Qatar on Friday announced it has shipped a consignment of liquefied natural gas as aid for the Egyptian people, in its first such gesture since president Mohammed Morsi's overthrow.

State news agency QNA said the LNG shipment was loaded on Thursday and was headed for Egypt on a gas tanker.