KIEV, Ukraine — The terrorist attack in New York on Tuesday was carried out by a young man from Central Asia, a former backyard of the Soviet Union known for poverty, isolation and repressive governments — all elements in breeding some of the most militant Islamist activity in the world.

Since the fall of the Soviet Union, Islamist insurgencies have erupted throughout the region, most notably in the Caucasus and the suspect’s native Uzbekistan. While those insurgencies have been mostly suppressed, often with unflinching brutality, analysts have grown increasingly concerned about Islamist radicalism spreading out of the region as young men leave in search of work.

This is particularly true, analysts say, of Uzbekistan, where a blend of repressive politics and economic failure has generated a steady outflow of both migrants and militants. Many of the immigrants have come to the United States — nearly 60,000 as of 2013, the American Community Survey said, with about half of them going to New York City.