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NEW YORK (NewsNation Now) — After a terrorist attack that killed 13 U.S. military members carried out by ISIS-K, there is concern that the upcoming 9/11 remembrance ceremonies could be under threat.

The Department of Homeland Security’s National Terrorism Advisory system warned 13 days ago that al-Qaida might be hoping to motivate U.S.-based individuals into committing extremist acts.

Though al-Qaida founder Osama bin Laden was killed by U.S. forces in 2011, officials say the group remains active, noting that al-Qaida in the Arabian peninsula recently released its first English-language copy of its “Inspire” magazine in more than four years.

New York City Mayor Bill de Blasio was asked about the threat to ceremonies commemorating the 20th anniversary of the 9/11 terrorist attacks. He said the city is watching the developments out of Afghanistan closely, but that he has no knowledge of a credible threat.

The NYPD Counterterrorism Bureau told that the organization is in a heightened state of alert.

Concerns about a domestic terrorist attack related to COVID-19 frustrations were also mentioned in the bulletin.

The heightened security bulletin will remain in effect until Veterans Day on Nov. 11, but could be extended based on security threats.