New satellite images show an increased use of heavy weapons in and
around Syria's city of Aleppo, raising urgent concerns over the welfare
of residents, Amnesty International has said.
The rights group says the photos reveal more than 600 craters, which were probably caused by artillery shells.
Both government troops and rebels may be held criminally responsible for failing to protect civilians, it warns.
Meanwhile, Iran has reiterated support for Syrian President Bashar al-Assad.
During talks in Damascus, Iran's security chief Saeed Jalili said Syria was part of a vital regional alliance that Tehran would not allow to be broken.
Jalili said Damascus was an essential part of an "axis of resistance".
Correspondents say "axis of resistance" refers to Iran, Syria, Hezbollah in Lebanon and the Palestinian Islamist group Hamas in Gaza.
Jalili's comments came a day after Syrian Prime Minister Riad Hijab defected to the opposition.
'Clear message'
In a statement, Amnesty says the new images in and around Aleppo "show an increased use of heavy weaponry, including near residential areas".
Some of the pictures, the group says, reveal "more than 600 probable artillery impact craters" from heavy fighting between government troops and rebel forces in the nearby town of Anadan.
In one case, Amnesty adds, a crater is seen next to what appears to be residential housing complex in the town.
"Amnesty International is sending a clear message to both sides in the fighting: any attacks against civilians will be clearly documented so that those responsible can be held accountable," said the group's US emergency response manager, Christoph Koettl.
"Turning Syria's most populous city into a battlefield will have devastating consequences for civilians. The atrocities in Syria are mounting already," he added.
Neither the government in Damascus, nor the rebels have publicly commented on Amnesty's claims.
However, independent experts the BBC has talked to agree with the group's interpretation of the images, the BBC's Mike Wooldridge reports.
'Intense attacks'
On the ground, new clashes were reported in Aleppo earlier this week and the army is said to have stepped up its bombardment of the northern city.
Government forces are trying to dislodge rebel fighters who say they control up to half of Aleppo.
Opposition activists report intense attacks on rebel-held areas on the north-east and south-west sides of the city.
State media said troops had clashed with "terrorists" in several places inflicting heavy losses.
British-based activist group Syrian Observatory for Human Rights said 61 civilians died in Aleppo province on Monday.
Further deaths were reported in Damascus on Tuesday. State news agency Sana said a "terrorist hideout" had been stormed by security forces.
Activists estimate more than 20,000 people have died since the uprising against President Assad began in March last year.
Reports of casualties often cannot be independently verified.
The rights group says the photos reveal more than 600 craters, which were probably caused by artillery shells.
Both government troops and rebels may be held criminally responsible for failing to protect civilians, it warns.
Meanwhile, Iran has reiterated support for Syrian President Bashar al-Assad.
During talks in Damascus, Iran's security chief Saeed Jalili said Syria was part of a vital regional alliance that Tehran would not allow to be broken.
Jalili said Damascus was an essential part of an "axis of resistance".
Correspondents say "axis of resistance" refers to Iran, Syria, Hezbollah in Lebanon and the Palestinian Islamist group Hamas in Gaza.
Jalili's comments came a day after Syrian Prime Minister Riad Hijab defected to the opposition.
'Clear message'
In a statement, Amnesty says the new images in and around Aleppo "show an increased use of heavy weaponry, including near residential areas".
Some of the pictures, the group says, reveal "more than 600 probable artillery impact craters" from heavy fighting between government troops and rebel forces in the nearby town of Anadan.
In one case, Amnesty adds, a crater is seen next to what appears to be residential housing complex in the town.
"Amnesty International is sending a clear message to both sides in the fighting: any attacks against civilians will be clearly documented so that those responsible can be held accountable," said the group's US emergency response manager, Christoph Koettl.
"Turning Syria's most populous city into a battlefield will have devastating consequences for civilians. The atrocities in Syria are mounting already," he added.
Neither the government in Damascus, nor the rebels have publicly commented on Amnesty's claims.
However, independent experts the BBC has talked to agree with the group's interpretation of the images, the BBC's Mike Wooldridge reports.
'Intense attacks'
On the ground, new clashes were reported in Aleppo earlier this week and the army is said to have stepped up its bombardment of the northern city.
Government forces are trying to dislodge rebel fighters who say they control up to half of Aleppo.
Opposition activists report intense attacks on rebel-held areas on the north-east and south-west sides of the city.
State media said troops had clashed with "terrorists" in several places inflicting heavy losses.
British-based activist group Syrian Observatory for Human Rights said 61 civilians died in Aleppo province on Monday.
Further deaths were reported in Damascus on Tuesday. State news agency Sana said a "terrorist hideout" had been stormed by security forces.
Activists estimate more than 20,000 people have died since the uprising against President Assad began in March last year.
Reports of casualties often cannot be independently verified.