Reports that former top White House aide Michael Flynn was part of a plot to help forcibly remove a Muslim cleric to Turkey are "false", his lawyer says.
Robert Kelner said claims that the ex-national security adviser and his son had met Turkish representatives to discuss a plot were "outrageous".
An alleged $15m (£11.5m) plan to remove cleric Fethullah Gulen was revealed by ex-fCIA director James Woolsey.
Turkey accuses Mr Gulen of being behind the failed July 2016 coup.
Turkish President Recep Tayyip Erdogan has repeatedly called for Mr Gulen's extradition from the US, where he lives in Pennsylvania.
According to The Wall Street Journal, Mr Flynn - who quit his post after misleading the White House about meeting a Russian envoy before Donald Trump took office - discussed having Mr Gulen transported on a private jet to the Turkish prison island of Imrali.
It also reported a payment was offered.
The newspaper said the matter had emerged as part of special counsel Robert Mueller's investigation into alleged Russian meddling in the US election.
The inquiry focused on a meeting in mid-December between Mr Flynn, who was serving on the White House transition team at the time, and Turkish officials in New York, it reported.
Meanwhile, NBC said that federal investigators were also looking into whether Mr Flynn had tried to push for the return of Mr Gulen to Turkey during his time as White House national security adviser.
But Mr Kelner vociferously denied all the allegations. He issued a statement saying that, as a rule, they had avoided responding to media rumours and allegations.
"But today's news cycle has brought allegations about General Flynn, ranging from kidnapping to bribery, that are so outrageous and prejudicial that we are making an exception to our usual rule: they are false," he added.
Ex-CIA chief Mr Woolsey, who is also a board member for Mr Flynn's consultancy, Flynn Intel Group, previously told CNN about a meeting involving Turkish officials in September 2016.
"There was at least some strong suggestion by one or more of the Americans present at the meeting that we would be able, the United States would be able, through them, to be able to get hold of Gulen," he said.
A spokesman for the company denied Mr Flynn had discussed any illegal actions with the officials.
Mr Flynn was the first aide in President Trump's White House to resign, after only 23 days on the job.
The retired lieutenant general had admitted lying to Vice-President Mike Pence about a meeting with the Russian ambassador in which the lifting of US sanctions was discussed.
Mr Flynn also failed to register as a lobbyist for the Turkish government while he was seeking White House security clearance.
In 2016, Flynn Intel Group was paid $530,000 for lobbying on behalf of the Turkish government - work which required him to register as "a foreign agent".
His lawyer later said Mr Flynn had not registered because he was working for a Turkish businessman, rather than a government official.
Investigators are also looking into the actions of his son, Michel Flynn Jr, who worked closely with him at Flynn Intel Group.
NBC News and The Wall Street Journal also reported that Mr Flynn and the meeting participants had discussed a way to free Turkish-Iranian gold trader Reza Zarrab, who is in a US jail on charges of evading US sanctions on Iran.