Syrian government and allied forces pressed an offensive on rebel-held eastern Aleppo for the fourth straight day on Friday, as the United Nations warned that basic supplies for the besieged population had all but run out. 

UN humanitarian adviser Jan Egeland said eastern Aleppo faces a "very bleak moment" with no food or medical supplies, little clean water and winter fast approaching. The UN had planned to deliver aid to a million people in hard-to-reach places across Syria in November, but so far not a single convoy has reached those in need, Egeland said, adding that both the government and rebels bore responsibility for blocking shipments.

More than 250,000 civilians have been trapped in eastern Aleppo since regime-aligned forces surrounded half the city in July. Opposition controlled areas of the city enjoyed a relative period of respite since October 18, when Russia and Syria announced a series of unilateral ceasefires and Moscow said it would refrain from bombing the city.

Russia and Syria said the ceasefires were designed to allow residents to flee, but few left. An alliance of rebels and jihadists used the lull in fighting to launch an offensive on government controlled western Aleppo, killing dozens of civilians before a government counterattack largely pushed the rebels back.  

The Syrian-government aligned forces launched one of the most vicious attacks on eastern Aleppo earlier this week, unleashing artillery fire and aerial bombardments that have killed at least 100 people since Tuesday, according to residents and monitors. 

Several hospitals, including a children's hospital, have been hit. According to the World Health Organization, there have been 126 attacks on hospitals so far this year. Other critical infrastructure has been targeted.

The Syrian regime aims to retake all of Aleppo, the country's largest city and commercial center before the war, which has been divided between rebels and government since 2012. Recapturing the city would be a major blow to rebels and jihadist factions.  

Russia, which intervened in Syria in September 2015 to support President Bashar al-Assad, has said its forces are not participating the offensive against eastern Aleppo. Instead, Russian warplanes and cruise missiles are targeting an alliance of rebels and jihadists in Idlib, Homs and northern Aleppo provinces.

cw/jm (AFP, AP, dpa, Reuters)