UN's Aleppo office 'directly targeted' in attack
"It is appalling that the building that houses the UN offices was directly targeted," the top UN official in Syria, Ali al-Za'tari, said in a statement on Monday.
"We strongly condemn the increased violence in all of Aleppo, east and west, which has resulted in the death and injury of scores of civilians, including children."
The UN statement did not report any injuries, nor did it specify how it was known to be a tank shell, rather than any other type of munition, or which side was responsible for firing the shell.
Rebel groups on Friday launched an assault on western Aleppo to try to break a siege on the eastern half of the contested city, where an estimated 275,000 people, and 8,000 rebels, are surrounded by forces loyal to President Bashar al-Assad.
According to the latest numbers from the Syrian Observatory for Human Rights, at least 53 civilians, including 18 children, have been killed and many more wounded by rockets launched by rebel groups.
The UN Special Envoy for Syria Staffan de Mistura on Sunday said he was "appalled and shocked" by the "indiscriminate" bombardment, which also destroyed a school.