BEIRUT (AP) — A halt in fighting announced by Russia to allow Syrian rebels and residents to leave the besieged eastern parts of Aleppo has gone into effect, with activists reporting a relative calm in the city.

The Britain-based Syrian Observatory for Human Rights says that during the early hours of the 10-hour "humanitarian pause" on Friday, it recorded no major military action by Syrian and allied forces or by the opposition fighters.

A pro-government Facebook news platform Aleppo Shahba News Network says designated corridors have been opened for the fighters and civilians but the Observatory says no one has used them so far.

Rebel spokesman Yasser Al-Youssef says helicopters are hovering over the area.

The U.N. estimates 275,000 people are trapped in the eastern, rebel-held part of the divided city of Aleppo.