WASHINGTON - The United States has assigned more than 1,000 spies to protect the Rio Olympics, US media reported.

According to an NBC News review of a highly classified report on US intelligence efforts, hundreds of analysts, law enforcement and special operations personnel, along with more than a dozen Navy and Marine Corps commandos, are currently working with the Brazilian Federal Police and the Brazilian Navy in Rio de Janeiro.

The report said that the operation involves all 17 US intelligence agencies, undertaking various jobs such as vetting athletes and security and police personnel, monitoring terrorists' social media accounts and helping secure computer networks.

"US intelligence agencies are working closely with Brazilian intelligence officials to support their efforts to identify and disrupt potential threats to the Olympic Games in Rio," Richard Kolko, a spokesman for US National Intelligence Director James Clapper, told NBC News.

Fifty-one countries are supplying intelligence to the Brazilian counter-terrorism effort for the Summer Olympic Games and the US operation is the biggest among the foreign contributors, according to NBC.

Security has been a major concern over the Rio Olympics. Earlier this month, authorities arrested over a dozen people who allegedly pledged allegiance to the Islamic State militant group.

On Saturday, a suspicious package was detonated at the Olympic cycle road race venue. Officials later confirmed that there was no impact to the race.