The Syrian regime is amassing troops in Aleppo in order to carry out a massacre, fears the US. President Bashar al-Assad's regime has deployed several tanks, helicopter gunships and fixed-wing aircraft which suggest preparation for a massacre, according to the US State Department.

Syrian forces have been on a massive offensive in the country's second largest city in the past few days. On 26 July, more than 100 people died in clashes in Aleppo, unconfirmed reports said.

"This is the concern, that we will see a massacre in Aleppo, and that's what the regime appears to be lining up for," said spokesperson Victoria Nuland. Aleppo is the most populous city in Syria and the commercial capital. Earlier, the Syrian regime had carried out massacres in Hama and Houla in a bid to crush the rebels.

Apparently referring to the continuing support by Russia and China to the Assad regime, Nuland said UN chief Ban ki-Moon also shares the US frustration that Security Council members have been rendered helpless.

The rebels too are piling up arms, ammunition and medical supplies fearing more attacks while the US is reportedly providing them communication equipment and medical help.

"Our hearts are with the people of Aleppo. And again, this is another desperate attempt by a regime that is going down to try to maintain control, and we are greatly concerned about what they are capable of in Aleppo," said Nuland. He ruled out military intervention in Syria without a mandate from the UN Security Council.

"The rebels have so far been nimble, and civilians have mostly been the victims of the bombardment. The regime is massing troops and tanks at the entrances of Aleppo, but it seems it is for now content with bombarding the city, with the rebels constantly on the move," activist Abu Mohammad al-Halabi told Reuters.

People also fear that makeshift arrangements like schools which have turned into relief camps will also be targeted by the regime's forces which could lead to a catastrophe.

Tens of thousands of Aleppo residents have already fled the city and the remaining civilians stay behind shut doors in their houses fearing attacks.