KABUL, Afghanistan — The number of aid workers killed in Afghanistan has more than tripled this year, making the country by far the most dangerous place in the world for relief work, according to data released by United Nations officials here.

Officials were reluctant to attribute the increase to any single factor. But in a number of recent cases, Taliban insurgents have openly claimed responsibility — despite espousing an official policy that rejects attacks on humanitarian workers.

“We are looking at the situation with concern about what are clearly increasing numbers of aid workers affected by the conflict,” said Mark Bowden, the humanitarian coordinator for the United Nations here.

Through November, he said, there were 237 attacks on Afghanistan’s aid workers, with 36 people killed, 46 wounded and 96 detained or abducted. Last year, there were 175 attacks, with 11 people killed, 26 wounded and 44 detained or abducted.