The UN agency has been working for many years in the region with refugees
A senior official of the United Nations refugee agency, John Solecki, has been kidnapped in the western Pakistani city of Quetta, the UN has confirmed.
Police said gunmen stopped his vehicle on his way to work, seizing him and killing his driver, a local man.
No group has claimed responsibility for the kidnapping.
Quetta is capital of Balochistan, where insurgents have been fighting for more autonomy. The Taleban are also active in the area, which borders Afghanistan.
In a statement, the UN condemned attacks on humanitarian workers and said all measures were being taken to secure Mr Solecki's release.
Pakistani police said roadblocks had been set up on the roads out of Quetta and on border crossings to Afghanistan.
Quetta police official Wazir Khan Nasir told Reuters news agency that the gunmen had taken Mr Solecki with them "after shooting his driver".
The man, a Pakistani, later died in hospital.
Television pictures from the scene of the incident showed a white vehicle with UNHCR markings rammed against a wall. At least one bullet hole was visible on the vehicle.
Quetta is the capital of Balochistan province, which borders Afghanistan.
The UNHCR has been working for years in Quetta with refugees from Afghanistan.
There has been low level insurgency in Balochistan driven by groups wanting more autonomy for the energy-rich province.
Taleban groups have also been active in the region and several of the group's leaders, including Mullah Omar, are believed to be in hiding in the city.
Kidnappings of foreigners have increased in Pakistan in the last year, says the BBC's Barbara Plett in the capital, Islamabad, but mostly occur in the north-west, where the Taleban are strongest.