The US Secret Service said it has dismantled a network of more than 100,000 SIM cards that could have crashed New York's telecommunications network ahead of the UN General Assembly, linking the threat to "nation-state" actors.
"In addition to carrying out anonymous telephonic threats, these devices could be used to conduct a wide range of telecommunications attacks," the agency said in a statement on Tuesday.
"This includes disabling cell phone towers, enabling denial of service attacks, and facilitating anonymous, encrypted communication between potential threat actors and criminal enterprises."
The UN's high-level general debate kicks off in New York on Tuesday, with US President Donald Trump due to address the summit on its first day.
The US Secret Service said the devices it seized were located within a 56-kilometre radius of the UN General Assembly.
"Given the timing, location and potential for significant disruption to New York telecommunications posed by these devices, the agency moved quickly to disrupt this network," the statement said.
It said that while forensic examination of the devices and a broader investigation were ongoing, "early analysis indicates cellular communications between nation-state threat actors and individuals that are known to federal law enforcement."
Images shared by the agency showed scores of SIM cards connected to telecommunications equipment.
