Pakistani police said the victim was the regional chief of the UN refugee agency in Quetta and a foreigner, but the United Nations declined to specify either his nationality or his rank at the UNHCR.
The official was snatched from his vehicle while travelling to work in Quetta, the provincial capital of energy-rich Baluchistan, where regional insurgency, sectarian violence and attacks blamed on the Taliban occur.
The UNHCR regional chief was on his way to office when ambushed by unknown gunmen, local Pakistani police official Khalid Masood told AFP.
They opened fire. His driver was wounded and died on the way to hospital, Masood told AFP.
The gunmen took him away to an unknown location, the police official added.
A white jeep, with the blue insignia of the UNHCR, had apparently veered off the road and smashed into a brick wall. A small pool of blood could be seen on the pavement next to the driver's door, said an AFP photographer.
Although a frequent hazard in northwest Pakistan, foreign kidnappings in Baluchistan are rare.
The last foreign abduction reported in Baluchistan was in 1991 when a group of Afghan fighters kidnapped three Chinese engineers and took them across the border into Afghanistan. They were later released.
A UN official confirmed only that a colleague working for the UNHCR had been kidnapped in Quetta.
I can confirm this unfortunate incident of a UN colleague's kidnapping this morning in Quetta and injuries to his driver, information officer Ishrat Rizvi told AFP by telephone in the Pakistan capital Islamabad.
The UN is working with police and concerned officials to ensure that all appropriate measures are taken to address this situation, she added.
A local aid worker in the area, speaking on condition of anonymity, told AFP that the kidnapped UNHCR officer was an expatriate.
Quetta city police chief Humayun Jogezai confirmed the incident and said paramilitary officers had been placed on standby.
We have alerted the Frontier Corps and they are ready to act swiftly on any tip-off about the man who has been kidnapped, he told AFP.
We will not waste a minute in raiding any place where we think this man is being held hostage, Jogezai said.
Another police official told AFP on condition of anonymity that religious elements may have been involved, adopting a euphemism for Islamist militants.
The driver of the UN vehicle was a Shiite, he said. Hundreds of people have died in insurgent violence in Baluchistan, on the border with Afghanistan, since 2004, when rebels rose up demanding political autonomy and a greater share of profits from the region's natural resources. But most kidnappings in Pakistan take place in the northwest. Gunmen kidnapped an Iranian diplomat, Hashmatullah Atharzadeh, and killed his local guard while he was on his to the consulate in Peshawar in November. A Canadian journalist was also abducted in November in Pakistan's northern tribal region. Suspected Taliban militants also kidnapped Afghan Consul General Abdul Khaliq Farahi near Peshawar nearly two months ago and are still holding him. Pakistan's military has been waging a major campaign in the tribal-dominated area against Taliban and Al-Qaeda militants, who are accused of launching attacks on international troops across the border in Afghanistan.