Special Counsel Robert Mueller III on Tuesday asked United States President Donald Trump’s former aide Steve Bannon (pictured above) to testify before a grand jury in connection with allegations about Russian meddling in the 2016 elections, The New York Times reported on Wednesday. Mueller, who is heading the investigation, subpoenaed Bannon on the same day the White House Chief strategist testified before a House Intelligence Committee, Bloomberg reported.

The Justice Department allows prosecutors to subpoena the targets of an investigation only in rare circumstances, The New York Times reported.

The former chief strategist refused to answer questions the House Intelligence Committee asked, Democratic Party member and intelligence committee member Adam Schiff told The Guardian. Schiff said the former Breitbart executive “was willing to answer our questions but under instructions from the White House not to.”

Bannon had a public falling out with Trump after he told Michael Wolff, the author of the book Fire and Fury: Inside the Trump White House, that the meeting between Donald Trump Jr, the president’s eldest son, and a Russian lawyer who claimed to have damaging information on Democratic Party’s presidential candidate Hillary Clinton was “treasonous” and “unpatriotic”. On January 10, Bannon had resigned from the right-wing website Breitbart News.