A suicide bomber killed at least 67 people and wounded dozens in an attack that struck a government-run hospital in the southwestern city of Quetta on Monday, police and doctors said.

Witnesses described horrifying scenes of bodies scattered on the ground the wounded screaming out for help. Hours after the attack, a breakaway faction of militant Taliban group claimed responsibility.

In a statement, Ahsanullah Ahsan, spokesman for Jamaat-ul-Ahrar militant group, also said their men killed Bilal Kasi, the president of Baluchistan Bar Association, and then targeted the mourners who had gathered at the government-run Civil Hospital. The group has been behind several attacks in Pakistan in recent years. The claim could not be independently verified.

Nearly 100 lawyers had gathered at the hospital in the heart of Quetta, the capital of Baluchistan province, after the body of Kasi, a prominent local attorney, was brought there.

Kasi was shot and killed by gunmen earlier on Monday as he was on his way to his office. The lawyers gathered at the Quetta Civil Hospital to express their grief as is common with public figures. Kasi was among the most outspoken lawyers in the province and was popular for campaigning for improvements in the legal community.

"It was a suicide attack," said Zahoor Ahmed Afridi, a senior police officer. Afridi said the attacker struck shortly after Kasi's body was brought in.

Abdul Rehman, the director at the Civil Hospital, said the bombing killed 67 people, mostly lawyers. He said they were also treating 92 wounded in the explosion. Two journalists working for Pakistani news channels were also killed in the attack, according to Shahzada Zulfiqar, the President of the Quetta Press Club.

One of the survivors described a horrifying scene, saying there were "bodies everywhere." Waliur Rehman said he was taking his ailing father to the emergency ward when the explosion shook the building, knocking them both to the ground.

Another witness, lawyer Abdul Latif, said he arrived at the hospital to express his grief over Kasi's killing. But he said he didn't know he would "see the bodies of dozens of other lawyers" killed and wounded shortly after arriving.

Sanaullah Zehri, chief minister in Baluchistan province, said both the bombing and Kasi's slaying seemed to be part of a plot to disrupt peace in the provincial capital.

Sarfraz Bugti, the provincial interior minister, denounced the attack as an "act of terrorism."

Local TV stations broadcast footage showing people running in panic around the hospital grounds. Afridi said most of the dead were lawyers.

Prime Minister Nawaz Sharif strongly condemned the blast and expressed his "deep grief and anguish over the loss of precious human lives."

"No one will be allowed to disturb the peace in the province that has been restored thanks to the countless sacrifices by the security forces, police and the people of Baluchistan," he said in a statement. Sharif asked the local authorities to maintain utmost vigilance and beef up security in Quetta.

Later Monday, the prime minister traveled to Quetta to meet the wounded and assess the situation.

Gen. Raheel Sharif, Pakistan's powerful army chief, also visited the hospital, and met with the wounded. According to a military statement, he ordered intelligence agencies to track down and apprehend all those linked to Monday's attack.

Ali Zafar, the head of the country's main lawyers' association, condemned the blast as "an attack on justice." He said lawyers will observe three days of mourning and will not appear in court in solidarity with their colleagues and others killed in the attack.

Quetta and the rest of Baluchistan province have long been hit by insurgency. There are several ethnic Baluch separatist groups operating in the resource-rich province, but al-Qaida, the Pakistani Taliban and other militant groups also have a presence here.

Lawyers have been targeted in the past by militants in various parts of Pakistan. They are considered an important part of civil society and emerged as powerful actors in 2007, when then-President Pervez Musharraf fired the Chief Justice Iftikhar Mohammad Chaudhry. Lawyers launched nationwide protests to pressure Musharraf to reinstate Chaudhry. Later, political parties joined the campaign and Musharraf was ultimately forced to resign in 2008 and Chaudhry was reinstated.