At least 26 children were killed in violence in Syria on Monday, a watchdog said, fuelling international calls for a war crimes probe into the 22-month conflict.
Reports of the child deaths came as Human Rights Watch accused President Bashar al-Assad's regime of expanding its use of banned cluster bombs.
Eight of the children were killed in an air strike on the town of Moadamiyat al-Sham, southwest of Damascus, the Syrian Observatory for Human Rights said. Five women were also killed.
"The children, all members of the same clan, were aged between six months and nine years old," said the head of the Britain-based Observatory, Rami Abdel Rahman.
State television blamed "terrorists" for the deaths.
Also near the capital, four other children were killed, including two siblings, the Observatory said.
Eight children were killed in the northern province of Aleppo -- five of them in an air strike.
Six more children died in other flashpoints in the strife-torn country.
The Observatory says that more than 3,500 children have been killed since the Syrian conflict erupted in March 2011. The United Nations says more than 60,000 people have died in all, while the Observatory reported at least 126 killed on Monday alone.
International medical organisation Medecins Sans Frontieres condemned a Sunday air stike on the Alppo province town of Aazaz that wounded 99 people.
"The attack... was particularly devastating as it came just two weeks after air strikes hit the city's health facilities, making it almost impossible for medical staff to cope with an emergency on this scale," MSF said.
On the diplomatic front, at least 57 governments called on the UN Security Council refer the Syria conflict to the International Criminal Court for a war crimes investigation.
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Switzerland sent a petition requesting the move to the 15-member council, the only body that can refer the case to the ICC but which is deeply divided over the conflict.
The signatories included many European governments as well as Libya and Tunisia, which both saw Arab Spring uprisings overthrow longstanding autocratic regimes.
The letter called on the Security Council to refer the Syria conflict for an ICC investigation "without exceptions and irrespective of the alleged perpetrators."
As Syria is not an ICC member, only a Security Council referral could start a war crimes investigation.
New York-based Human Rights Watch said other governments should sign up to the Swiss-led initiative.
"Human Rights Watch urged other states, particularly Arab states who have repeatedly voiced concern over the killings in Syria, to join the mounting calls for accountability," the organisation said in a statement.
But diplomats said the council's divide on Syria is so deep that no move by the body is now possible.
Russia and China, both veto-wielding permanent council members, have refused to sign the petition.
On Sunday, Russia said Assad's removal from power was not a part of past international agreements on the crisis and so impossible to implement.
The wrangling comes amid warnings that the conflict, which according to the UN has sent more than 600,000 Syrians fleeing into neighbouring countries, is growing more dangerous for civilians in the face of the regime's expanded use of cluster bombs.
Syria "is now resorting to a notoriously indiscriminate type of cluster munition that gravely threatens civilian populations," the director of HRW's arms division Steve Goose said in a statement.
UN-Arab League peace envoy Lakhdar Brahimi, who last week dismissed peace proposals by Assad as "one-sided", came in for more criticism from the Syrian authorities with government daily Al-Thawra describing him as an "ageing tourist".