A nationwide ceasefire in Syria, brokered by the United States and Russia, has come into effect.

It is the second attempt this year by Washington and Moscow to bring an end to the five-year-long civil war.

Shortly before the week-long truce started, violence was reported in several areas throughout the country.

Under the terms of the deal, if it lasts for a week, Russia and America will co-ordinate attacks against some rebel groups including Islamic State and al-Qaeda's former Syria branch known as the Nusra Front.