Islamic State has begun distributing increasingly long “kill lists” of ordinary Americans purportedly encouraging its followers to target those individuals, vexing authorities who are at odds over whether the lists pose an actual threat or are merely scare tactics.

A list distributed late last month contained the names of more than 2,000 New Yorkers, while another listed about 1,500 Texans. None of the people had known connections to government or to issues that the terror group cares about, according to counterterrorism officials.

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