Fighting raged in several Syrian flashpoints on Wednesday as key Damascus ally Moscow lashed out the opposition for its "obsession" with toppling President Bashar al-Assad.
In a related development, Russian President Vladimir Putin offered to host an international conference aimed at aiding the more than 650,000 refugees the UN says have fled the 22-month conflict.
The Syrian Observatory for Human Rights said six members of one family -- a couple and four children -- were killed in a dawn missile attack on the village of Abu Taltal in Aleppo province, updating an earlier count of five.
In a video released by activists, the bodies of the three children, a boy and two small girls, can be seen lying on blankets on a hospital bed.
Their brightly coloured clothes are stained with blood and their faces are turned away from the camera.
The Observatory has previously reported more than 3,500 child deaths in Syria's conflict.
In Ras al-Ain, in the Kurdish northeast, battles raged between Kurdish militia and Islamist rebels, the Observatory said, adding that more than 58 people have been killed in a week of fierce fighting there.
Wednesday's violence killed at least 48 people, according to a count by the Observatory. The UN says more than 60,000 people have died since the conflict first erupted in March 2011.
In Moscow, Foreign Minister Sergei Lavrov criticised Syria's opposition for its "obsession" with toppling Assad, and warned of a long conflict.
"For now, everything is running up against the opposition's obsession with toppling Bashar Assad's regime," Lavrov told reporters.
"As long as this irreconcilable position remains in place, nothing good can happen. Armed actions will continue and people will die."
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He said the opposition's insistence on ousting Assad was stymying efforts to find a diplomatic solution backed by the former international peace envoy Kofi Annan and his successor, Lakhdar Brahimi.
In a telephone conversation with Brahimi, UN Secretary General Ban Ki-moon and Arab League chief Nabil al-Arabi pledged "total support" for the envoy as he struggles to launch political talks to try to end the civil war.
Brahimi, criticised by Assad's government, has so far failed to bring key players Russia and the United States in line behind a transition plan.
Some diplomats and analysts have speculated that Brahimi, whose six-month mandate comes up for renewal in February, might be considering his future.
The developments came as Human Rights Watch warned that rebel groups appeared to have destroyed or allowed the looting of minority religious sites in northern Syria.
"The destruction of religious sites is furthering sectarian fears and compounding the tragedies of the country," said Sarah Leah Whitson, Middle East director at New York-based HRW.
Whitson spoke of both Shiite Muslim and Christian targets.
And as the UN said that more than 650,000 people have fled Syria to neighbouring Jordan, Lebanon and Turkey, Russia's Putin offered to host an international conference in Moscow on the refugee crisis.
"If the interested nations agree to this, we will be ready to propose Moscow as the venue," news agencies quoted him as saying.
Meanwhile, the UN Food and Agriculture Organisation warned that Syrian agriculture has been shattered by the conflict, putting the livelihoods of about half the country's population at risk.
"Twenty-two months of conflict has left Syria's agricultural sector in tatters, with cereal, fruit and vegetable production dropping for some by half and massive destruction of irrigation and other infrastructure," a statement said.
The UN says about 46 percent of the population derives its livelihood from agriculture.