Kabul

KABUL — A blizzard of bank notes is flying out of Afghanistan — often in full view of customs officers at the Kabul airport — as part of a cash exodus that is confounding U.S. officials and raising concerns about the money’s origin.

The cash, estimated to total well over $1 billion a year, flows mostly to the Persian Gulf emirate of Dubai, where many wealthy Afghans now park their families and funds, according to U.S. and Afghan officials. So long as departing cash is declared at the airport here, its transfer is legal.

But at a time when the United States and its allies are spending billions of dollars to prop up the fragile government of President Hamid Karzai, the volume of the outflow has stirred concerns that funds have been diverted from aid. The U.S. Drug Enforcement Administration, for its part, is trying to figure out whether some of the money comes from Afghanistan’s thriving opium trade. And officials in neighboring Pakistan think that at least some of the cash leaving Kabul has been smuggled overland from Pakistan.

“All this money magically appears from nowhere,” said a U.S. official who monitors Afghanistan’s growing role as a hub for cash transfers to Dubai, which has six flights a day to and from Kabul.

Meanwhile, the United States is stepping up efforts to stop money flow in the other direction — into Afghanistan and Pakistan in support of al-Qaeda and the Taliban. Senior Treasury Department officials visited Kabul this month to discuss the cash flows and other issues relating to this country’s infant, often chaotic financial sector.

Read moreUS officials puzzle over millions of dollars in cash, well over $1 billion a year, leaving Afghanistan by plane for Dubai