WASHINGTON (REUTERS) - US authorities thwarted plots to kill people in the United States around the July 4 holiday, FBI director James Comey said on Thursday.

Comey told reporters more than 10 people inspired by the Islamic State in Iraq and Syria's recruitment online have been arrested over the past four weeks, with some focused on attacks around the July 4 holiday.

The Federal Bureau of Investigation and the Department of Homeland Security issued a warning to local law enforcement to be on the alert for attacks around July 4.

No such attacks occurred.

Comey did not give details on the number of plots thwarted or their targets.

He said dozens of people in the United States who are suspected to be under the influence of Islamic State militants have "gone dark" because of encrypted data.