sentence1: ISLAMABAD, Pakistan (CNN) -- Taliban militants made their deepest incursion into Pakistan this week, seizing control of areas that are a short drive from the capital city.  A Pakistani government official said the militants fully withdrew from the Buner district on Friday, although other officials cast doubt on the extent of the pullout and how long it would last. Buner is only 60 miles outside Islamabad. The situation is particularly concerning because Pakistan is a nuclear-armed state. The Islamic republic is believed to have between 30 and 40 nuclear warheads, according to the U.N. nuclear watchdog, the International Atomic Energy Agency (IAEA).
sentence2: Pakistan's nuclear arsenal creates concerns.