Secretary of State John Kerry rebuked the Syrian Assad regime for carrying out “nothing short of a massacre” in Aleppo, as tens of thousands of civilians were held in the recent siege of the rebel stronghold.

Mr Kerry called for an “immediate, verifiable, and durable cessation of hostilities” and urged both Syrian President Bashar al-Assad and Russian leaders to participate in direct negotiations with the United Nations in Geneva.

“There is absolutely no justification whatsoever for the indiscriminate and savage brutality against civilians shows by the regime and by its russian and iranian allies over the past few weeks and, indeed, over the past five years,” he said at a press briefing on Thursday.

Mr Assad appeared on Syrian state television earlier in the day to proclaim victory and celebrate what he referred to as the “liberation” of Aleppo. He said by defeating “terrorists” was “history in the making”.

Non-combatant activists recorded their harrowing accounts and shared over social media, including Twitter and WhatsApp.

We spoke to the last activists in Aleppo. They're waiting to die

“We are [given] only two deadly choices: Death or displacement. Both of them are heartbreaking,” said English teacher Abdulkafi Alhamdo in a tweet at dawn.

Aleppo before the Syrian Civil War Show all 12 1 /12 Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man crosses a street in Aleppo, December 12, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A vendor sits inside an antique shop in al-Jdeideh neighbourhood, in the Old City of Aleppo, December 12, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A view shows part of Aleppo's historic citadel, overlooking Aleppo city, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A view shows part of Aleppo's historic citadel, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Visitors walk inside Aleppo's Umayyad mosque, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk inside the Khan al-Shounah market, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man walks past shops in al-Jdeideh neighbourhood, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk along an alley in al-Jdeideh neighbourhood, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Visitors tour Aleppo's historic citadel, Syria December 11, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A general view shows the Old City of Aleppo as seen from Aleppo's historic citadel, Syria December 11, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk near Aleppo's Bab al-Faraj Clock Tower, Syria October 6, 2010 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man stands inside Aleppo's historic citadel, overlooking Aleppo city, Syria December 11, 2009 Reuters

Another activists stuck in east Aleppo wrote on WhatsApp: “Anyone who knows anything about the Assad regime should know what to expect. Death will be a wish for those captured and deemed [to be] opposition, [whether] military or civil.”

Following a Wednesday night ceasefire agreement, prompting an evacuation of fighters and civilians. However, the first fleets of buses have only been able to transport a few hundred, and a significant evacuation could take a number of days.

Mr Kerry said that the stabilisation of Aleppo is top priority. That must occur if officials expect to carry out meaningful peace negotiations.

“Provided we are able to stabilise the situation in Aleppo,” he said, “it is essential that we move forward at the earliest possible moment with a Syrian-led political process aimed at ending the war and transitioning to a new, more representative government.