KABUL — The United Nations said Thursday that it will send more than half its international staff either out of Afghanistan or into more secure compounds following last week’s deadly Taliban attack against U.N. workers — the most direct targeting of its employees during decades of work in the country.

The head of the U.N. mission also issued a stern warning to newly re-elected President Hamid Karzai that Afghanistan can no longer count on international support unless he cracks down on corruption and initiates reforms.