Syrian President Bashar al-Assad has appeared on state television to address the people of Aleppo on the “liberation” of the city.

Driving the last “terrorists” out was “history in the making”, and “greater than the word ‘congratulations’,” he said.

Evacuations of fighters and civilians from the last rebel areas of the city began on Thursday after a ceasefire deal was struck on Wednesday night. Approximately 200 left in the first batch of 17 buses, and a second convoy left in the afternoon, but the slow pace means it could be days before the target of 5,000 people is reached.

It is unclear how many people are left in the last slivers of rebel-held territory in the east of the city. The UN has put the figure as high as 50,000, but critics say that is an overestimate. Rebel fighters, among them al-Qaeda affiliated factions, are among the number.

“Thousands of people are in need of evacuation but the first and most urgent thing is wounded, sick and children, including orphans,” Jan Egeland, the UN’s humanitarian adviser for Syria, told reporters in Geneva.

Fierce ground fighting and incessant air strikes have killed hundreds in the divided city since Mr Assad’s forces stepped up the campaign to retake the last urban rebel stronghold two weeks ago. The UN and other international agencies condemned reports that government-allied Shia Iraqi militias had gone from house to house shooting up to 82 civilians, including women and children, on Monday.

Foreign Secretary Boris Johnson has summoned the Russian and Iranian ambassadors to the UK – Syria’s main allies – over his “profound concern” in the still volatile situation.

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

Trapped residents, who have lived under siege conditions since July, were given a brief respite on Tuesday night when a first truce was brokered by Russia and Turkey. However, the deal collapsed in less than 12 hours, dashing their hopes of reaching safety.

Many are treating the second attempt at a ceasefire with caution, although the first convoy is reported to have reached neighbouring rebel-held Idlib without incident.

Wissam Zarqa, an English teacher in the rebel zone, said most people were happy to be leaving safely, but added: “Some of them are angry they are leaving their city. I saw some of them crying. This is almost my feeling in a way.” Mr Zarqa said he will stay in east Aleppo as long as he can.

At least one White Helmets volunteer was shot and killed by a sniper while clearing the road of rubble for ambulances to pass this morning, temporarily halting the evacuation plans.

Syria conflict: Aleppo civilians post 'goodbye' videos

Aleppo, once Syria’s economic powerhouse and home to several Unesco World Heritage Sites – has become the epicentre of Syria’s bloody civil war. Recapturing the city is a major victory for Mr Assad, relegating Sunni rebel opposition to the far north and south of the country, and removing the last fighters from Syria’s cities.

However, the six-year-long war is far from over, observers say, with the opposition likely to evolve into an insurgency movement. Isis is also far from defeated, launching a surprise attack to retake the ancient city of Palmyra last week.

The International Rescue Committee and other organisations have called for a countrywide ceasefire, noting that Idlib province, where the Aleppo buses are headed, has also been hit by heavy air strikes in recent months.