Air strikes hit rebel-held areas of Aleppo, monitors say
Four air strikes have hit rebel-held parts of the Syrian city of Aleppo, activists say, the first raids there since a ceasefire began last Monday.
Several people were injured, the UK-based Syrian Observatory for Human Rights said, but it did not say who carried out the strikes.
Russia has said the future of the truce is in doubt after the US-led coalition struck the Syrian army in Deir al-Zour.
A Syrian political adviser told the BBC the US strike could not be a mistake.
The cessation of hostilities brokered jointly by the US and Russia does not exclude attacks on IS or other jihadist groups.
An activist in Aleppo confirmed there had been strikes on the eastern neighbourhoods of Karam al-Jabal and al-Shaar.
The Aleppo Media Centre reported three injuries in an air strike on al-Sakhour neighbourhood.
The US-led attack on Saturday caused tensions between the US and Russia, with both Russia and Syria accusing the US of co-ordinating the strikes and the Islamic State group.
The US military said the coalition believed it was attacking IS positions, and has expressed regret for the "unintentional loss of life".
But President Bashar al-Assad's media adviser Bouthaina Shaaban said she did not believe the attack was unintentional.
"The United States, the superpower, the greatest country in the world, makes mistakes in targeting the army? I mean, this doesn't make sense to ask," she told BBC World television.
"The other explanation is that there is one authority in the United States who wanted to conduct this, the other doesn't want to. And that's why they are finding it very difficult to implement what they agreed upon with the Russian," she said.
The attack put "a very big question mark" over the truce's future, said Russia's UN Ambassador Vitaly Churkin.
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But French Foreign Minister Jean-Marc Ayrault said that despite the US-led strike the Syrian government was mostly to blame for the violations of the truce.
Syria said on Sunday it had lost a warplane in the area of Saturday's attack, which so-called Islamic State (IS) said it had shot down.
The BBC's Lina Sinjab, reporting from neighbouring Lebanon, says it is rare for the Syrian government to acknowledge losses caused by IS, and the announcement may be intended to draw attention to the consequences of the US-led air strike.
The air attack caused a bitter row between the US and Russia at the United Nations Security Council on Saturday night, with each country's representatives walking out while the other was speaking.
Analysis by BBC diplomatic correspondent Jonathan Marcus
Washington's mistaken air strikes on Syrian government forces raise several questions; not least why American aircraft were hitting what they thought were IS positions in an area where IS was engaged with Syrian forces.
The US role is clearly not directly to assist Mr Assad's troops against IS fighters.
The strikes, belatedly called off after the Russians notified the Americans, have made a delicate situation even more complex.
They have put at risk a ceasefire that, so far, is only partial and that has not yet provided the promised access for aid deliveries to begin in earnest.
The error - admitted by the Pentagon - is bound to erode what limited trust, if any, exists between Washington and Moscow. If the ceasefire does survive, that is going to make implementing any plans for a coordinated US-Russian air campaign against IS that much harder.
Only if the current ceasefire, which started on Monday, holds for seven days, will the US and Russia begin co-ordinated action against the Jabhat Fateh al-Sham group, which was previously known as the al-Nusra Front, and IS.
The deal was meant to allow the safe passage of aid to besieged areas of Syria, but some 20 trucks have been waiting in Turkey since Monday, unable to travel to rebel-held east Aleppo.
The Syrian truce
- A deal was brokered by Russia and the US that began with a nationwide ceasefire from Monday between the armed opposition and the Syrian government, but not jihadist groups
- The ceasefire will be renewed every 48 hours if it holds
- It is meant to allow for "unimpeded and sustained humanitarian access" to besieged areas, including Aleppo
- If the truce holds for a week, Russia and the US will bomb militant groups together, including so-called Islamic State and Jabhat Fateh al-Sham (formerly the Nusra Front)
- The "legitimate opposition" are meant to distance themselves from such groups
- The deal has faced widespread scepticism, not least because the US backs anti-government rebel groups while Moscow is a key ally of the Syrian government
- The deal could pave the way for a political transition, the US says