The United Nations has raised its security level for the Pakistani capital following the Sept. 20 truck bombing of the Marriott Hotel, U.N. officials said Thursday.

The move underlines the deteriorating situation in Pakistan, which is under intense U.S. pressure to combat Islamic militants responsible for rising attacks at home and in neighboring Afghanistan.

U.N. Secretary-General Ban Ki-moon approved the move after the world body's agencies in Islamabad recommended it earlier this week, three officials told The Associated Press.

They said it also applied to the neighboring city of Rawalpindi and areas near the Afghan border.

The officials spoke on condition of anonymity either because they are not authorized to speak to the media or did not want to go on the record before an expected official announcement from U.N. headquarters in New York.

The decision means that U.N. international staff will no longer be allowed to live with their children in the capital. Some can relocate to areas deemed safer, such as Lahore or Karachi.

Others are expected to leave Pakistan, which is likely to cause some disruption to U.N. programs as the country faces severe economic difficulties and a crumbling of basic public services in militancy-torn areas.

Foreign missions have also been reviewing security since the Marriott bombing, which killed at least 54 people, including three Americans and the Czech ambassador.

Britain announced Wednesday that about 60 children of its diplomats in Pakistan will return home. Pakistan has long been a non-family posting for U.S. Embassy staff.

Pakistani officials have blamed the Marriott blast on extremists holed up in tribal areas along the Afghan border who are suspected of mounting a wave of suicide attacks stretching back more than a year.