Gunmen kidnapped two U.N. workers on Monday while they were travelling in a lawless Pakistani region near the Afghan border, a U.N. official said.

The two workers for the U.N. World Food Programme were abducted on their way to the Afghan border, travelling through the Khyber region where Pakistan's ambassador to Afghanistan was kidnapped in February. He is still being held.

"Negotiations are underway. We hope to have some positive development by the evening," said the U.N. official who declined to be identified.

The two are Pakistanis. A guard travelling with them was also seized, the official said.

A government official in the region said police were searching for the three men and their abductors.

"They were whisked away by unidentified gunmen," said the government official who also declined to be identified.

"Some policemen at a nearby post spotted them and are following them," he said.

Pakistan's ambassador to Afghanistan, Tariq Azizuddin, went missing in the same region while travelling to Kabul on Feb. 11.

He appeared in a video on Arabic television on Saturday saying he was being held by the Taliban and urged the Pakistani government to meet their demands.

Scores of people have been kidnapped in the dangerous border region between Afghanistan and Pakistan and the ambassador's disappearance highlighted instability in nuclear-armed Pakistan - a major ally in the U.S.-led crackdown on militants.