Just days before President Trump was sworn in, his former national security adviser, Michael Flynn, reportedly blocked a military plan opposed by Turkey that was supposed to take aim against an ISIS group.

The plan that he reportedly blocked was to be carried out by Syrian Kurdish forces in Raqqa, a measure Turkey has long opposed.

Flynn, who was fired from his position in February, was registered as a foreign agent for $530,000 worth of lobbying work before Election Day.

Paperwork filed in March with the Justice Department's Foreign Agent Registration Unit said Flynn and his firm were voluntarily registering for lobbying from August through November that "could be construed to have principally benefited the Republic of Turkey."

The McClatchy news service reported that President Obama’s national security team asked for Trump’s approval on a plan to retake the Islamic State’s de facto capital of Raqqa, because it was more than likely to be carried out under his presidency.

Timelines distributed by members of Congress show that Flynn told then national security advisor Susan Rice to hold off, delaying the operation for months.

Trump eventually approved the plan, but only after Flynn had been fired in February for misleading Vice President Mike Pence and other white House officials about his ties to Russia’s ambassador to the U.S.

It was only weeks later in March when Flynn disclosed to the Foreign Agent Unit Registration Unit of the Justice Department that he was paid for work that “could be construed to have principally benefited the Republic of Turkey.”

News about Flynn's activity comes amid intense scrutiny over his and other Trump associates' potential contacts with Russia. On Wednesday, the Department of Justice named former FBI Director Robert Mueller to be special counsel investigating Russian efforts to influence the U.S. presidential election. Mueller will have sweeping powers, including the right to bring federal charges.

House and Senate intelligence committees are also investigating.

The Associated Press contributed to this report.