Air strikes on rebel-held areas of Syria have reportedly killed at least 100 people hours after the US and Russia announced plans for a truce to begin in the next two days.
An air strike on a market in Idlib killed up to 60 people while at least 45 died in strikes on Aleppo province, opposition activists said.
Some of the air strikes were believed to have hit the towns of Anadan and Hreitan near Aleppo.
If the planned 10-day ceasefire - due to take effect in the next two days - holds for a week, the US and Russia hope to coordinate air strikes against Islamist extremists.
Turkey and the EU welcomed the plan but warned that further action was needed.
Turkey said aid must be delivered from the very start while EU foreign policy chief Federica Mogherini looked towards a "political transition".
A spokeswoman for Syria's opposition said the plan provided some hope but more details were needed about how it would be enforced.
In the capital, Damascus, the government endorsed the deal, the state news agency Sana reported.
There has been no official reaction from Iran which, like Russia, is allied to Syrian President Bashar al-Assad.
If the truce holds...
- Jihadist groups like Islamic State and Jabhat Fateh al-Sham (formerly known as Nusra Front) would face the joint might of the Russian and US air forces
- Moderate rebels and civilians in the areas they hold would no longer face the threat of indiscriminate air strikes such as barrel-bombing, although the Syrian air force would not be grounded completely; aid deliveries will be allowed to areas currently under siege
- President Assad would be in a stronger position as the US and Russia engage two of his most effective military opponents while moderate rebels observe the truce with his forces
The conflict in Syria, which began with an uprising against Mr Assad, has raged for five years and claimed the lives of more than a quarter of a million people.
Millions have fled abroad, many of them seeking asylum in the EU, but nearly 18 million people remain in Syria, which has been carved up by fighting between government and rebel forces.
When a busy vegetable market was targeted in Idlib, about 90 people were injured in addition to those killed, media and opposition activists say.
Some of Saturday's air strikes are believed to have hit the towns of Anadan and Hreitan near Aleppo, Syria's second city.
Mr Lavrov said only the Russian and US air forces would operate in areas designated for co-ordinated strikes but added that the Syrian air force could operate in other areas.
Welcoming the deal, Turkey, which launched its first major military incursion into Syria last month, said it was essential to halt fighting across Syria and deliver humanitarian aid to those in need "from the first day".
"The agreement ... is very welcome," said Ms Mogherini, stressing that a UN proposal for a political transition would be "the starting point for resumption of the intra-Syrian talks".
Previous diplomatic initiatives have foundered on President Assad's refusal to give up power, leading to widespread scepticism about the latest initiative.
NZ welcomes ceasefire
Foreign Affairs Minister Murray McCully welcomed the ceasefire announced yesterday by the US Secretary of State John Kerry and the Russian Foreign Minister Sergei Lavrov.
Mr McCully said the next few days would be crucial to see if the ceasefire held.
He urged all parties to return to negotiations on a permanent end to the war and a political transition.
As President of the United Nations Security Council, New Zealand will host a Leaders' meeting to discuss Syria on the 21st September, which the Prime Minister John Key will chair.
US envoy warns rebels
Washington's envoy to Syria warned the country's mainstream rebels that cooperation with Fateh al-Sham, formerly al Qaeda's Nusra Front, could bring "dire consequences" for them once the proposed US-Russian deal to attack hardline extremists comes into effect.
In a letter to armed opposition groups seen by Reuters, Michael Ratney urged them to abide by the deal, saying it gave them the right of self-defence against attacks by the Syrian army and Russia.
The deal would end aerial bombardment by Russia and the Syrian air force of their positions and of civilians living in areas they control, he said.
The fighting in Syria, which began with an uprising against Mr Assad, has raged for five years and claimed the lives of more than a quarter of a million people.
Millions have fled the country, but nearly 18 million people remain in Syria, which has been carved up by fighting between government and rebel forces.
-BBC / Reuters