Federal agents delivered grand jury subpoenas to New York Times reporters at their homes, U.S. outlets including Fox News reported, in a probe of leaks behind reporting on the new 747-8 presidential aircraft from Qatar.

Directly subpoenaing reporters collides with source-protection norms and is rare even in the U.S. Press groups warn of a chilling effect on newsgathering.

The Times is said to be weighing legal options and stressing the public interest of its reporting; the administration calls it a legitimate national-security leak investigation.

Tensions between the administration and major outlets have simmered for months; the subpoenas move that conflict into the courts.

A legal battle over the line between First Amendment protections and leak inquiries now looks likely.