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.

Jamaatul Ahrar emailed a statement to media warning of more attacks, which the group’s spokesman said would “continue until implementation of sharia (Islamic law) in Pakistan.”

Meanwhile, Islamic State said its cell in the region of Khurassan, which straddles Pakistan and Afghanistan, was responsible for the attack, a source close to the group told dpa.

Islamic State has been behind previous attacks in Pakistan, but this is the first one it claimed in Balochistan, the largest of the country’s provinces and one rich in minerals.

Militant groups in Pakistan often compete in claiming their role in major attacks. At least three outfits said they were behind the attack at the Wagah border crossing with India in 2014 in which more than 55 people died.

Lawyers’ associations announced seven days of mourning and a one-day boycott of courts across the country to protest the attack.

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.

The United States condemned the suicide-bomb attack on a hospital in Quetta, Pakistan, that killed at least 70 people on Monday.

“Today, terrorists targeted a hospital, as well as the judiciary and the media, two of the most important pillars of every democracy,” State Department spokeswoman Elizabeth Trudeau said in a statement. “These brutal and senseless attacks only deepen our shared resolve to defeat terrorism around the world.”

“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.