At least 53 people were killed when a bomb exploded at the main gate of a government-run hospital in south-western Pakistan, officials said.

Noor Ahmed, a deputy chief surgeon for victims of violent crime, said the hospital in the city of Quetta is also treating about 50 people who were wounded in the blast on Monday.

No-one has yet claimed responsibility for the attack.

Quetta is the capital of Baluchistan province, which has witnessed deadly attacks in recent years.

Sanaullah Zehri, the chief minister in Baluchistan, said it seemed to be a suicide attack but police are still investigating.

Senior police official Zahoor Ahmed Afridi said the bomb went off shortly after the body of a prominent lawyer killed earlier in the day was taken to the hospital.

It was also unknown who was behind the killing of the lawyer, Bilal Kasi, who was gunned down on his way to court.

Police official Afzal Khan said dozens of lawyers and journalists were present inside the hospital when the bomb went off.

Pakistan's prime minister denounced the hospital attack.

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 wounded in the attack.

Mr 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.