A suspected US missile struck a car carrying alleged terrorists in a northwest Pakistan tribal region Friday, killing three men in the second such attack in less than a day, intelligence officials said. The strikes are part of the US campaign to rid Pakistan of a creeping terrorist movement Washington believes is threatening the war effort in neighboring Afghanistan. The rising insecurity inside Pakistan, meanwhile, is prompting the United Nations to relocate about a quarter of its international staff in the country, officials confirmed Thursday. Both missile strikes occurred in North Waziristan, a lawless tribal region along the Afghan border that is home to several militant groups that tend to focus on attacking US and NATO forces in Afghanistan. The one Friday happened near Mir Ali, a major town in the region, said two intelligence officials who spoke on condition of anonymity because they were not authorized to speak on the record. Shortly after Friday's attack, Taliban arrived at scene of the attack in the village of Ghundi and moved the bodies to an undisclosed location, the officials said. The United States has fired scores of missiles from unmanned drones into Pakistan's tribal regions since 2008 in a campaign primarily targeting al-Qaida. US officials rarely discuss the strikes, and Pakistan publicly condemns them though it is widely believed to aid them secretly. Pakistan is in the midst of an army offensive against the Taliban in South Waziristan, an operation that has spawned a wave of revenge attacks across the country in a bloody campaign that has killed more than 500 people since October. At least 11 UN workers have been killed in Pakistan over the past year, and the organization had already reduced its activities in the country's volatile northwest in response to the deteriorating conditions before Thursday's announcement of a partial pullout. UN security managers are seeking a reduction of up to 30 percent in the UN's international staff working inside Pakistan, a UN official told The Associated Press on condition of anonymity because security details and negotiations are confidential. However, the actual number is likely to be lower and will depend on negotiations with the various UN agency heads who oversee those workers, the official said. The UN employs about 250 international and 2,500 national staff in Pakistan. The official said an undetermined number of national staff will likely be moved out of Pakistan's North West Frontier Province, or NWFP, along the border with Afghanistan, and from the western province of Baluchistan. The UN scaled back its operations in Baluchistan in July after a threat by separatists who kidnapped an American aid worker. In Islamabad, spokeswoman Ishrat Rizvi said around 20 percent of the UN's expatriate workers will either leave Pakistan for six months or be relocated to safer areas within the country. She declined to give specifics on what projects or employees would be affected. The UN began reviewing its operations after an October attack on the World Food Program office in Islamabad killed five people. The goal was to see how it could operate more effectively and safely in Pakistan without disrupting its relief and development aid. UN operations in Pakistan since early 2009 have grown to some $1 billion for the nation's "sustainable development" needs, officials said. Since spring they have also handed out some $475 million in emergency humanitarian aid in northern Pakistan.