At least 42 people were killed when a bomb exploded at the main gate of a government-run hospital in south-western Pakistan, police said.
Senior police official Zahoor Ahmed Afridi said dozens of other people were injured in the blast in the city of Quetta on Monday.
No-one immediately claimed responsibility for the attack.
Afridi said the bomb went off shortly after the body of a prominent lawyer who was shot dead earlier in the day was taken to the hospital.
Sanaullah Zehri, the chief minister in Baluchistan province, of which Quetta is the capital, said it seemed to be a suicide attack but police are still investigating.
It was also unknown who was behind the killing of the lawyer, Bilal Kasi, who was gunned down on his way to court.
Pakistan's prime minister denounced the hospital bombing.
Nawaz Sharif issued a statement expressing his "deep grief and anguish over the loss of precious human lives".
He instructed local authorities in Baluchistan province to maintain utmost vigilance and beef up security. He also asked health workers to provide the best treatment possible to those injured in the attack.
Sharif added that "no-one will be allowed to disturb the peace" which "countless sacrifices" by the "security forces, police and the people of Baluchistan" have worked so hard to restore.