Police say a former lawyer for the Pakistani doctor who helped the US find Osama bin Laden has been killed by armed men in the country's northwest.
Shakir Khan, a senior police officer, said unidentified assailants shot and killed Samiullah Khan Afridi on Tuesday in Peshawar before fleeing.
The killing comes just months after he announced that he will no longer be representing Dr Shakil Afridi, who was convicted in May 2012 of "conspiring against the state" by giving money and providing medical treatment to fighters, not for helping the CIA track down bin Laden.
The lawyer left Pakistan in November after receiving threats from fighters.
Khan said the lawyer recently came back from abroad.
Ahsanullah Ahsan, a spokesman for the Pakistani Taliban-linked Jamaat-ul-Ahrar group, claimed responsibility for Tuesday's killing in an emailed statement to Pakistani news media and in a telephone call to the Associated Press news agency from an unidentified location.
The statement said: "The Tehreek-e-Taliban Pakistan Jamaat ur Ahrar accepts responsibility for the attack on Samiullah, the lawyer of Shakil Afridi, who was co-operating with the killers of Sheikh Osama bin Laden. The enemy should remember that we will kill each and every one of the killers of each of our brothers."
Dr Afridi ran a vaccination campaign in the northwestern city of Abbottabad as a cover for a CIA-backed effort to obtain DNA samples from a home where bin Laden was later killed during a 2011 raid by US navy SEALs.
Polio workers killed
In an earlier incident on Tuesday, also in northwestern Pakistan, armed men killed two female polio workers and a police guard.
Police said two attackers fired at the workers as they gave polio drops to children in the mountainous Sheikhabad area, 60km northeast of the city of Mansehra.
"The two-member team was administering polio drops in an Afghan refugee camp and its surrounding areas when two gunmen opened fire on them, killing one lady worker and a policeman and wounding another lady worker and a passer-by," Muhammad Ejaz Khan, local police chief, told AFP news agency.
He said the second woman polio worker later died of her wounds.
Akhtar Hayat, another senior local police official, confirmed the incident and casualties.
Pakistan is one of only three countries where polio remains endemic.
Attempts to eradicate it have been badly hit by attacks on immunisation teams that have claimed 77 lives since December 2012.
The attackers claim the polio-vaccination drive is a front for espionage or a conspiracy to sterilise Muslims.
Last year the number of polio cases recorded in Pakistan jumped to 306, the highest in 14 years.
Source: Al Jazeera and agencies