The United Nations said on Monday it plans to contact the United States over a report that the U.S. National Security Agency bugged its New York headquarters and warned that countries are expected to respect the world body's diplomatic inviolability.

Citing secret U.S. documents obtained by fugitive former intelligence contractor Edward Snowden, Germany's Der Spiegel reported on Sunday that the United States succeeded in gaining access to the internal U.N. video conferencing system in 2012.

"We're aware of the reports and we intend to be in touch with the relevant authorities on this," U.N. spokesman Farhan Haq told reporters.