Washington: The US National Security Agency collected 534 million records of phone calls and text messages of Americans last year, more than triple gathered in 2016, a US intelligence agency report released on Friday said.

The sharp increase from 151 million occurred during the second full year of a new surveillance system established at the spy agency after US lawmakers passed a law in 2015 that sought to limit its ability to collect such records in bulk.

The records collected include the numbers and time of a call or text message, but not their content.

The NSA has collected millions more records since a law was passed in 2015 to curb its bulk surveillance. Credit:AP

The spike in collection of call records coincided with an increase reported on Friday across other surveillance methods, raising questions from some privacy advocates who are concerned about potential government overreach and intrusion into the lives of American citizens.