Several foreign aid groups suspended their operations in Balochistan on Sunday and moved staff out of the region after threats of attacks from an al Qaeda-linked militants, officials said.
"We have suspended our operation and shifted about a dozen foreign staff members to hotels or other safer places," UN High Commissioner for Refugees (UNHCR) spokesman Babar Baloch told AFP.
Police said around 18 other foreigners, including US and British nationals, working with various non-government organisations (NGOs) had also moved out of the region, which borders Afghanistan.
Intelligence officials had received information that a former Taleban militant was planning suicide attacks on UNHCR offices in Quetta and the border town of Chaman, Provincial police chief Chaudhry Yaqub said.
The information said the militant might also be planning attacks on other NGOs in the region with British or US nationals on their staff, he said.
The militant was identified as Maulvi Hashim Ishaqzai, who is said to have links with the al-Qaeda terror network that was sheltered by the hard-line Taleban regime.
The information was conveyed to these involved organisations with instructions to take necessary precautionary measures, Yaqub said.
"Such reports do come to us frequently and we take preventive measures," he said. "There is nothing alarming. We have taken necessary security measures."
Home ministry officials said the NGOs had been asked to restrict the movement of their staff and secure an escort from the authorities if they went on trips for fieldwork.
In a letter to the aid groups, the government liaison office for Afghan relief agencies said, "It is reliably learnt that a group of Taleban headed by one Mullah Hashim Ishaqzai ... is planning to target the UNHCR office and other foreign NGOs at Quetta and other parts of Balochistan through suicide bomb attacks."
"Only those NGOs will be targeted where US or British nationals are working," the letter said, advising the organisations concerned to "beef up security."
The UNHCR spokesman said the agency, which helps Afghan refugees return to their country would resume its operations in the region only on the advice of its security officials in Islamabad.
"We cannot resume our work unless we are advised by UN security officials in Islamabad. They are in touch with us and discussions are on with government officials," Baloch said.