Gunmen in Pakistan on Tuesday killed a former lawyer for the doctor who ran a fake vaccination program to help the U.S. locate Osama bin Laden, police said.

Senior police officer Shakir Khan said unidentified assailants shot and killed Samiullah Khan Afridi in the northwestern city of Peshawar before fleeing.

Afridi was killed months after he announced that he would no longer represent Dr. Shakil Afridi (they are not related), who was convicted in May 2012 of “conspiring against the state” by giving money and providing medical treatment to militants, not for helping the CIA track down bin Laden.

The lawyer left Pakistan late last year after receiving threats from armed groups and had recently returned, Khan said.

A spokesman for the Taliban-linked Jamaat-ul-Ahrar group, Ahsanullah Ahsan, claimed responsibility for the killing in a telephone call to The Associated Press from an unidentified location.

Afridi, the doctor, was accused of running a fake program of hepatitis vaccinations in the Pakistani city of Abbottabad, just north of the country's capital. Leon Panetta, the former U.S. defense secretary, confirmed in 2012 that Afridi had worked for U.S. intelligence by collecting DNA samples to help locate bin Laden.

U.S. forces killed bin Laden in May 2011 in a raid on his hideout in Abbottabad, ending a nearly 10-year hunt following the Sept. 11, 2001 attacks on the U.S.

In May 2012, Dr. Afridi was sentenced to 33 years under the Frontier Crimes Regulations, or FCR, the set of tribal laws that govern Pakistan's semi-autonomous tribal region.

Human rights organizations have criticized the tribunals for not providing suspects adequate due process. There is no right to legal representation, to cross-examine witnesses or to present evidence.

Reports following Afridi's conviction contradicted the notion that his ties to the U.S. had been the basis for his conviction. Court documents revealed that he was convicted for his ties to the banned group of fighters Lakshar-e-Islam, which operates in northwest Pakistan’s Khyber Agency.

"This appears to be an effort to patch things up with the United States, while also satisfying the people of Pakistan that Afridi has been punished," Mansur Mehsud, director for research at the FATA Research Center, an independent think tank based in Islamabad, told Reuters after Afridi’s conviction.

The White House announced last year that the CIA would stop using vaccination programs as a cover to gather intelligence — a tactic that has been widely criticized by humanitarian aid agencies operating in conflict zones around the world since the fake vaccination program came to light in 2011.

In 2012, the United Nations suspended a polio vaccination effort in Pakistan after gunmen killed several health workers. Taliban militants accused health workers of acting as spies for the U.S.

The CIA's use of a vaccine program to help locate bin Laden undercut the message of Obama's own high-profile speech to the Muslim world in 2009, in which he touted U.S. efforts to help eradicate polio in Pakistan, Afghanistan and Nigeria. With Obama administration assurances, Muslim scholars in two international groups issued religious decrees urging parents to vaccinate their children.

Al Jazeera and wire services