More than 180 people were killed in Syria on the first day of the country's partial ceasefire, over half of them in an Islamic State attack in the north of the country, a monitoring group said.
The Islamic State onslaught on the Kurdish-held border town of Tel Abyad and nearby towns and villages killed 70 jihadists, 20 Kurdish fighters and 10 civilians, the Syrian Observatory for Human Rights said.
Elsewhere in the country, 25 civilians were killed in shelling and gunfire.
Separately, one person died as a result of torture in a government facility and two others died due to the lack of food and healthcare in the besieged Damascus suburb of Daraya, the Observatory said.
Limited clashes in various parts of the country between government forces, rebels and Islamic State jihadists also cost the lives of over 50 combatants on the various sides, according to the Observatory, which compiles information from a network of activists across Syria.
The Russian- and US-backed ceasefire went into effect at midnight on Saturday local time (2200 GMT Friday).
Under its terms, groups who have signed up to it should not be attacked, but action against UN-designated terrorist organizations such as Islamic State and Syrian al-Qaeda branch the al-Nusra Front is still allowed.
Russia and the US have set up a mechanism to exchange information on the locations of groups who are taking part in the ceasefire.