Gunmen wounded an Egyptian working for the United Nations Children's Fund when they fired on his vehicle in Pakistan's largest city on Sunday, police said.
The motive for the attack was not entirely clear, but police said it may have been a robbery gone wrong.
The shooting followed an attack in July when two men working on the World Health Organization's polio campaign were wounded. Taliban fighters oppose the campaign and many religious leaders say it is a Western conspiracy to spy on or sterilize Muslims.
On Sunday three international U.N. workers were leaving a restaurant in Karachi's wealthy Clifton suburb when gunmen approached them, said Fayyaz Laghari, the provincial Inspector General.
As they drove off, the gunmen pursued them and opened fire, he said. An Egyptian working for the United Nations Children's Fund was shot in the shoulder, he said. It was not clear which agency the other two men worked for.
The port city of Karachi is Pakistan's financial hub and home to 18 million people.
Deadly shootings are a daily occurrence and the city is plagued by an epidemic of violent crime. It is also home to a number of sectarian groups and fighters allied to the Taliban insurgency.