Egypt is to shorten its night-time curfew by two hours, pushing back the start time to 9:00 pm (1900 GMT) except on Fridays, the premier's office said on Saturday.

"To lessen the burden on citizens and respond to popular request, the length of the curfew will be shortened and will begin at 9:00 pm instead of 7:00 pm," it said in a statement.

The curfew will continue to end at 6:00 am, the statement said, adding that the changes would go into effect immediately but would not apply on Fridays.

Friday is a traditional day of protests, which usually begin after weekly Muslim prayers in the afternoon.

Egyptian authorities imposed the night-time curfew on 14 provinces on August 14, after violence erupted as security forces cleared supporters of ousted Islamist president Mohamed Morsi from two protest camps in Cairo.