A new UN report says the humanitarian situation in Syria is worsening and the number of people needing urgent help has now reached 10.8 million - almost half of Syria's population of 22 million.

The finding came as UN Secretary General Ban Ki-moon called on the Security Council to impose an arms embargo on the country.

The report, obtained by Al Jazeera, shows that 10.8 million people are now in need of humanitarian assistance, among whom five million were difficult or impossible to reach.

The UN chief blamed foreign powers for supplying weapons to warring parties and fuelling the three-year conflict.

"I am here to express my anger and disappointment at the cold calculation that seems to be taking hold - that little can be done except to arm the parties and watch the conflict rage," Ban said.

"I urge the Security Council to impose an arms embargo. If divisions in the Council continue to prevent such a step, I urge countries to do so individually whatever they can to impose this arms embargo. Syria’s neighbours should enforce a firm prohibition on the use of their land borders and airspace for arms flows and smuggling into Syria,” he said.

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The UN chief also reported severe levels of violence including intensified use of barrel bombs by government forces against civilian areas, suicide attacks and reported executions by armed groups.

Meanwhile, the Syrian government cautioned the UN Security Council that delivering humanitarian aid across its borders into rebel-held areas without its consent would amount to an attack, suggesting it would have the right to retaliate against convoys.

"The sole purpose of the initiative is to use United Nations auspices for the delivery of logistical backing to the terrorists," Syria's UN Ambassador Bashar Jaafari said in a letter.

Source: Al Jazeera and agencies