All UN offices in Pakistan will close for three days from Wednesday as a security precaution with the world body set to release a report on the assassination of ex-premier Benazir Bhutto.
A United Nations panel, which began its investigations last July, was due to submit its findings to UN Secretary General Ban Ki-moon on March 31.
Bhutto, the first woman to become prime minister of a Muslim country, was killed on December 27, 2007 in a gun and suicide attack after addressing an election rally in Rawalpindi, a garrison city near the capital Islamabad.
Her supporters cast doubt on an initial Pakistani probe into her death, questioning whether she was killed by a gunshot or the blast and criticising authorities for hosing down the scene of the attack within minutes.
"Offices are going to be closed for the next three days. All UN offices in the country," spokeswoman Ishrat Rizvi said on Tuesday, saying that staff are being advised to work from home in a bid to avoid any possible fallout.
"It's a precautionary measure to avoid any unwanted situation that may occur after the publication of this report, for the safety and security of staff members," she added.
On October 5, a suicide bomber dressed in military uniform attacked the heavily fortified UN World Food Programme office in Islamabad, killing five staff members.
Security is precarious in parts of Pakistan, where more than 3,150 people have been killed in suicide and bomb attacks over the last three years. The violence has been blamed on militants opposed to the government's US alliance.
"These are internal arrangements, there is no threat. It is a precautionary step," Rizvi stressed.
The UN's investigative team has met dozens of people since first visiting Pakistan last July to probe the circumstances surrounding the attack.
The three-member panel is headed by Chilean ambassador to the UN Heraldo Munoz and aided by Indonesian ex-attorney general Marzuki Darusman and Peter Fitzgerald, an Irish former police official.
The commission questioned former president Pervez Musharraf in November on issues central to its mandate and met Bhutto's widower, President Asif Ali Zardari last month while finalising the report.
Musharraf, who was in power at the time of Bhutto's death, was replaced in August 2008 as president by Zardari, whose party called for a UN inquiry to probe inconsistencies surrounding her killing.
But the UN team has stipulated that its mandate is limited to fact-finding and does not include a criminal investigation.
London's Scotland Yard, which also conducted an inquiry, ruled that Bhutto died from the force of a suicide bomb and not gunfire.
The commission's report will be shared with the Pakistani government and the UN Security Council.