The United Nations Fund for Children has denounced the increase of violence in Syria, adding that children are paying a terrible price as the near two-year-old conflict drags on.

"UNICEF condemns these latest incidents in the strongest terms, and once again calls on all parties to ensure civilians - and children especially - are spared the effects of the conflict," the UN agency said on Saturday.

"A series of reports from Syria this week underlines the terrible price children are paying" in a conflict that has convulsed the country for 22 months and left more than 60,000 people dead, according to UN figures.

Maria Calivis, UNICEF regional director for the Middle East and North Africa, said: "Media reports today [Friday] from the scene of mass killings in the village of Hasweya outside Homs said whole families were among the dead in horrific circumstances."

More than half of the more than 600,000 refugees who have sought refuge from the Syrian conflict in neighbouring countries are under the age of 18 and the number of people fleeing could almost double by June, a senior UN official has said.

"This is a children's refugee crisis. It's heartbreaking when we see these children arriving and particularly what we see in the days that follow," Panos Moumtzis, the UN refugee agency (UNHCR) regional co-ordinator for Syrian refugees, said.

The Syrian Observatory for Human Rights, which relies on a network of activists and medics fort its information, has documented 3,538 children killed since the start of the revolt in March 2011. It also gave a toll of 2,031 women killed in the violence.

A UN delegation, including some UNICEF representatives, has arrived in the capital, Damascus. It is touring areas around the city, and places hit by some of the worst violence, like Homs and the village of Hasweya.

Earlier this week, activists reported 106 people - including many women and children - were burnt alive in their homes in the village.

There are conflicting reports about who is responsible.

Daraya shelling

Meanwhile, fighting has continued in the suburbs around Syria's capital.

Activists reported heavy shelling on Daraya, with as many as 80 explosions heard there on Saturday morning.

They said the blasts followed several air attacks by government forces.

Rebels are still in control of Daraya, but the regime has been fighting hard to take it over for about two months.

In another Syria-related development, Navi Pillay, the UN high commissioner for human rights, cited the country's increasing casualty count as a basis for an International Criminal Court investigation into war crimes.

"I firmly believe that war crimes and crimes against humanity have been committed, are being committed, and should be investigated," she said as 58 countries called for a war crimes case against Syria, in a letter to the president of the UN Security Council.

Pillay told Al Jazeera that people in Syria "see the situation as the United Nations not carrying out its responsibility to protect victims".

Syria's foreign ministry criticised the petition, saying the initiative was proof of the "deceit and double standards" of the signatories.