ALEPPO  - Rebels unleashed barrages of mortar fire against troops in the battleground city of Aleppo on Friday, residents said, as Washington unveiled new funding for humanitarian aid and the civilian opposition.

“The fighting is unprecedented and has not stopped since Thursday. The clashes used to be limited to one or two blocks of a district, but now the fighting is on several fronts,” the Syrian Observatory for Human Rights said. Residents of neighbourhoods previously spared the worst of the two-month-old battle for the northern city of Aleppo, Syria’s commercial capital, also told AFP the violence was unprecedented. “The sound from the fighting... has been non-stop,” said a resident of the central district of Sulamaniyeh, who identified himself as Ziad. “Everyone is terrified. I have never heard anything like this before.” Rebels claimed they had advanced on several fronts, particularly in the southwest, but admitted they had failed to make any significant breakthrough.

“On the Salaheddin front, we took one of the regular army bases,” said Abu Furat, one of the leaders of the Al-Tawhid Brigade, the most important in the city. But he admitted the fighters had to retreat from Salaheddin because they were outgunned. “To win a guerrilla street war, you have to have bombs and we don’t,” he said.

The Observatory which gave initial estimates of 65 people killed across the country on Friday - half of them civilians - said at least five civilians and five rebels died in Aleppo. By Friday afternoon the intensity of the fighting abated.

The Observatory’s head Rami Abdel Rahman said the fighting was not yielding major gains for either side: “Neither the regime nor the rebels are able to gain a decisive advantage.”

In New York, US Secretary of State Hillary Clinton unveiled a total of $45 million dollars in new funding for humanitarian aid and to help the civilian opposition in Syria.

Some $30 million will go towards aid, bumping up the total US funding for humanitarian relief to $130 million with a further $15 million for the civilian Syrian opposition, she told a meeting of the Friends of Syria.

The UN Human Rights Council, meanwhile, announced that renowned former war crimes prosecutor Carla Del Ponte is to join a UN probe into rights abuses during the conflict in Syria.

Clinton also said that Iran would do “whatever it takes” to prop up its ally in Damascus. “There is no longer any doubt that Iran will do whatever it takes to protect its proxy and crony in Damascus,” she told the Friends of Syria meeting.

In Washington, US Defence Secretary Leon Panetta said the Syrian regime has moved some chemical weapons to safeguard the material but the main storage sites for its arsenal remain secure.

“There has been some intelligence that with regards to some of these sites there has been some movement ...in order for the Syrians to better secure the chemicals,” Panetta told reporters. “We still believe, based on what we know and what we’re monitoring, that the principal sites remain secure,” he said.

On the ground, violence on Friday also raged in Damascus where troops attacked several rebel areas in both the north and the south of the capital, leaving three civilians dead, the Observatory said. Undeterred, thousands of protesters took to the streets of Aleppo and other cities in support of the unification of the rebel Free Syrian Army as factionalisation appears to undermine the anti-regime revolt.

The Observatory said demonstrations were held after the main weekly Muslim prayers in the Fardus and Sukari neighbourhoods of Aleppo, as well as in the central province of Homs, Hama further north and Idlib in the northwest.

The conflict has dominated proceedings at the UN General Assembly in New York, where UN and Arab leaders expressed concerns the country could become a “regional battleground.”

UN Secretary General Ban Ki-moon, Arab League leader Nabil al-Arabi and special envoy Lakhdar Brahimi shared those fears as they met at UN headquarters to discuss “the appalling levels of violence,” a UN spokesman said.