Turkey lashed out against Syria as the death toll from a missile strike on Aleppo rose to 58, while a US official urged the opposition to reconsider its boycott of international meetings.
France meanwhile confirmed that a French photographer wounded in the conflict had died of his injuries.
"Every day a large number of innocent children and women fall dead in Syria," Turkey's Prime Minister Recep Tayyip Erdogan said on Sunday during a visit to the United Arab Emirates.
"We will not remain silent on those committing crimes against their people.... We will not remain silent on the brutal dictator in Syria," Erdogan, a key backer of Syria's opposition, added.
Turkey's southern neighbour has been locked in a 23-month-long conflict in which the United Nations estimates more than 70,000 people have been killed.
On Sunday alone, according to a toll compiled by the Syrian Observatory for Human Rights, at least 105 people were killed in violence across the country.
The Britain-based monitoring group also updated its death toll from Friday's missile attack on the northern city of Aleppo, saying it killed at least 58 people, including 36 children.
Early in the revolt against President Bashar al-Assad's regime, Turkey broke ties with Damascus. It led international calls for Assad's ouster, has offered shelter to defectors from the army and hosted opposition meetings.
About 200,000 Syrian refugees have fled to Turkey, many of them living in squalid camps.
A senior US official on Sunday urged the Syrian opposition to rethink its decision to pull out of the 11-nation Friends of Syria meeting in Rome this Thursday, which new US Secretary of State John Kerry will attend.
"We are stressing... that they have an opportunity in Rome, to see the countries that have been their greatest supporters and to present to all of us how they see the situation on the ground in security, humanitarian, political and economic terms," said the official.
Already Saturday Washington had condemned the Assad regime for the Aleppo strikes.
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The attack was "the latest demonstrations of the Syrian regime's ruthlessness and its lack of compassion for the Syrian people it claims to represent", said State Department spokeswoman Victoria Nuland.
She repeated Washington's call for Assad to step down.
National Coalition chief Ahmed Moaz al-Khatib said early Saturday they were pulling out of the Rome meeting to protest at the "shameful" inaction of the international community in the face of civilian killings in Syria.
In Paris, the foreign ministry confirmed that freelance photographer Olivier Voisin, 38, seriously wounded by shrapnel from a shell in Syria on Thursday, had died of his injuries after surgery in Turkey.
"France once again pays homage to the work of journalists who risk their lives for freedom of expression," French Prime Minister Jean-Marc Ayrault said in a statement.
His death takes the number of reporters killed in Syria to at least 21, according to a count by AFP and Paris-based media watchdog Reporters Without Borders.
On Sunday the army used tanks to shell the Tariq al-Bab district in eastern Aleppo, the Observatory said.
Activists said prominent Syrian comedian Yassin Bakush was killed after a shell hit his car in a war-torn district of southern Damascus.
The jihadist Al-Nusra Front claimed responsibility for a suicide attack on an army factory earlier this month in the central city of Hama that killed at least 60 people.
And in northern Syria on Sunday, rebels closed in on a police academy in the town of Khan al-Assal in Aleppo province, as warplanes bombarded their positions there, the Observatory said.
The rebels already have large swathes of northern Syria under their control.
In Jordan Sunday, a policeman and two Syrian children were injured when refugees rioted at the Zaatari camp in the north of the country. Police used tear gas to disperse them, a government official said.
Since it opened in July the camp, which houses more than 90,000 Syrian refugees, has seen frequent protests, mainly over poor living conditions.