The bomber struck a crowd of some 200 people gathered at the Civil Hospital in Quetta after the fatal shooting of a senior local lawyer earlier in the day.
At least 70 people died in the attack and more than 100 were wounded.
“The targeting of mourners at a civilian hospital makes the attack particularly appalling,” said Ban’s spokesman Farhan Haq.
Ban urged the Pakistani government to do its utmost to bring those behind the attack to justice.
At least 70 people died when a suicide bomb tore through a crowd of mourners gathered at a Pakistani hospital Monday, in an attack claimed by both the Taliban and Islamic State group.
Prime Minister Nawaz Sharif called for security forces to “decimate” terrorists after the blast at the Civil Hospital in the Balochistan provincial capital Quetta, which also wounded more than 100 people.
Video footage showed bodies strewn on the ground among pools of blood and shattered glass as shocked survivors cried and tried to comfort one another.
The bomber struck a crowd of some 200 people that had gathered to mourn the death of a senior local lawyer who had been assassinated earlier in the day.