Police Officers Guarding Polio Workers Killed in Karachi, Pakistan

ISLAMABAD, Pakistan — Gunmen killed seven police officers guarding polio workers in twin attacks in Karachi, Pakistan Wednesday, according to officials.

Image: Karachi attack
Security personnel gather around a police van after the attack by gunmen in Karachi, Pakistan, on Wednesday. ASIF HASSAN / AFP - Getty Images

"These were trained assassins," said Feroz Shah, the city's deputy chief of police.

He said three of the officers, who were all wearing bulletproof jackets, died at the scene after being shot at close range in the head and neck. Four others died on the way to the hospital, he added.

None of the health workers were killed in the attacks, in the working-class suburb of Orangi Town, Senior Superintendent of Police Arif Meher said.

"We are treating this as a hit targeting police," he added.

Pakistan is one of the last countries where polio, which causes paralysis and death, is still endemic. Dozens of people have been assassinated in a drive by militants to prevent vaccinations. Health teams in many parts of the country travel with armed guards.

Related: Bomb Blast Kills 14 at Polio Center in Pakistan

The killings were claimed by a Taliban splinter group of the Pakistani Taliban, Tehreek-e-Taliban Pakistan Jamaatul Ahrar (TTP-JA).

"Both the police and polio workers are on our hit list as we consider polio vaccination against the Islamic sharia and will therefore kill them wherever we find them," the group's spokesman, Ehsanullah Ehsan, told NBC News on the telephone.

TTP-JA also claimed responsibility for a suicide attack at children park in Lahore on that killed at least 73 people on March 27.

The Taliban and some clerics have come out against the vaccinations, accusing polio workers of being spies for the U.S. and claiming they are part of a Western plot to sterilize children.

Attacks on vaccination teams grew after Pakistani doctor Shakil Afridi was arrested on charges of running a fake hepatitis vaccination campaign in Abbottabad as a cover for a CIA-backed effort to obtain DNA samples from a home where Osama bin Laden was later killed by U.S. Navy SEALs.

FROM NOV. 30, 2014: Pakistan's Polio Epidemic Aided by Anti-Vaccine Sentiment 2:49

Prime Minister Nawaz Sharif's office swiftly condemned Wednesday's killings and vowed to continue with the vaccination campaign.

"The prime minister offered his condolences to the bereaved families and prayed for the eternal peace of the departed souls," the statement read. "The entire nation will fight against these cowards with unity and ... resolve."

Police posted a $50,000 reward for information identifying the suspects.