Rights groups condemn UN inaction as 12 reported killed in Damascus

In separate calls this week, an international human-rights organisation and a group of legal experts have urged the United Nations to do more in Syria.

The New York-based Human Rights Watch called on Tuesday for the UN Security Council to block the flow of weapons to Syria's regime, which it said was launching indiscriminate attacks with "barrel bombs".

The group said it had documented 85 aerial attacks by the regime against opposition areas in northern Aleppo province since 22 February alone. It urged the United Nations to block the flow of arms to the government and any group committing abuses against civilians in the war-torn country.

"The Security Council should impose an arms embargo on Syria's government, as well as on any groups implicated in widespread or systematic human rights abuses," HRW said.

HRW's demands followed a letter from 35 legal experts published in several major US newspapers on Monday, said the "blantant disregard" for international humanitarian law by the Syrian government and elements of the opposition has caused millions to suffer. However, the experts said, the UN's approach to tackling the humanitarian crisis has been "overly cautious."

"[T]his appalling situation has been compounded by what we deem to be an overly cautious interpretation of international humanitarian law, which has held UN agencies back from delivering humanitarian aid across borders for fear that some member states will find them unlawful," the letter said.

Violence continues across the country, where an estimated 150,000 people have been killed in the past three years. On Tuesday, Syrian state TV reported that 12 people had been killed and 50 injured in shelling at the Badr al-Din al-Hussein technical institutes in the Shaghur neighborhood in the Old City of Damascus.

The statement from HRW comes more than two months after a 22 February Security Council resolution demanding an end to attacks on civilian areas.

HRW said that since then, it "has documented at least 85 strike sites in [opposition-held] neighbourhoods of Aleppo city... including two government barrel bomb attacks on clearly marked official hospitals".

The strikes, most reportedly involving "unguided, high-explosive barrel bombs", have hit civilians and civilian objects "indiscriminately".

The group said attacks that cannot distinguish between fighters and civilians are "unlawful".

Such attacks "continue despite a United Nations Security Council Resolution unanimously passed on 22 February, demanding that all parties in Syria cease the indiscriminate use of barrel bombs and other weapons in populated areas," HRW said.

Syrian government forces started aerial offensives targeting opposition areas last 15 December.

Hundreds of people have been killed in these attacks. Thousands of families have also fled into the countryside and for neighbouring Turkey to the north.

HRW's statement also came a day after President Bashar al-Assad registered to stand for re-election next month.

"President Assad is talking about elections, but for Aleppo's residents, the only campaign they are witnessing is a military one of barrel bombs and indiscriminate shelling," HRW deputy Middle East and North Africa director Nadim Houry said.

The rights group said the supply of arms to rebel groups that have committed systematic abuses must also stop.

It said that "at least some of the improvised weapons used (by rebels fighting an offensive on government areas in Aleppo) are prone to indiscriminate effects when used to attack populated residential areas".