Taliban gunmen attacked policemen guarding medical workers administering polio vaccinations in the Pakistani city of Karachi on Wednesday, killing seven of them.
While militants in Pakistan have on numerous occasions attacked teams trying to eradicate the crippling childhood disease, a police chief said his men were target this time, not the health workers.
The policemen were killed in two attacks in the sprawling port metropolis of more than 20 million people that has been plagued by ethnic, sectarian and political violence for years.
The attacks took place within 600 meters (650 yards) of each other near a market, a senior police official said.
"One took place at the three policemen who were escorting a polio team, the policemen were on foot when they were attacked," said the official, Ali Asif. "In the second incident, four policemen in a police van were targeted."
Provincial police chief Allah Dino Khwaja said the vaccination workers were not the target of the gunmen.
"The target was purely the police," he said.
The Pakistani Taliban claimed responsibility.
A spokesman for the group, Qari Saifullah Saif, said eight members carried out the attacks in revenge for the alleged killing of their colleagues by police in Karachi.
Teams in Pakistan working to immunize children against the virus are often targeted by Taliban and other militant groups, who say the campaign is a cover for Western spies, or accuse workers of distributing drugs designed to sterilize children.
At least 89 people – including vaccination workers and policemen – have been killed in such attacks since July 2012, according to a Reuters tally based on United Nations figures and media reports.
Last year, Pakistan reported 54 of 74 worldwide cases of polio, down drastically from the 306 cases reported in the country the year before, mainly due to expanded immunization efforts.
Government officials in Karachi said the immunization drive would be suspended while the violence was investigated.