Threats have been made against the United Nations in Lebanon in recent weeks and the world body is stepping up security in the country, a UN envoy said.
Michael Williams, the outgoing UN special coordinator for Lebanon, gave no details of the recent threats but cited two roadside bombs targeting the UN peacekeeping force in Lebanon, one that injured six French peacekeepers on July 26 and one that wounded six Italian peacekeepers on May 27.
The attackers have not been caught and could strike again at the force or other UN targets, he told a news conference.
The Lebanese army also shared "some credible reports" with the UN "of potential threats in the past few weeks," Mr Williams said.
UN Secretary-General Ban Ki-moon ordered a global review of UN security arrangements after a car crashed into the main United Nations building in Nigeria's capital, Abuja, and exploded on August 26, killing at least 23 people and wounding 81.
"There are risks as everybody knows," Mr Williams said. "There's an abundance of weaponry in Lebanon and there has been a history over the years, tragically, of terrorist attacks."
As a result, he said, the United Nations will be leaving the Beirut headquarters of the UN Economic and Social Council for West Asia, known as ESCWA, because of the dangers it poses - its front facade is almost entirely glass and its location is on a little island near two main thoroughfares.
Williams, who took up his post in October 2008, said the 2006 ceasefire that ended the war between Israel and Hezbollah militants "has held well and has provided southern Lebanon with the longest period of stability not in years but in decades".
The reinforced presence of UN peacekeepers and the deployment of the Lebanese army in the south for the first time "have contributed in great measure to the success" of the UN resolution that ended the fighting, he said.
Mr Williams, who plans to take up his seat in Britain's House of Lords after returning to London this weekend, added: "It is my firm belief that neither Israel nor Lebanon wishes to see a further conflict."