Police in Brazil have arrested lawyer José Yunes, who is a close friend and ex-advisor to President Michel Temer.
Mr Yunes was detained over corruption allegations surrounding the awarding of concessions at Brazil's busiest container port, which he denies.
President Temer himself is under investigation for allegedly issuing a decree which benefited a logistics firm in the port in exchange for bribes.
The president has denied any wrongdoing.
Mr Yunes's arrest was part of a larger federal police operation which saw five other influential figures also arrested.
The jailing of Mr Yunes, a lawyer with 50 years experience, was "an attack on Mr Yunes and the people [of Brazil", his lawyer said.
Among those arrested is another close friend of President Temer, João Batista Lima, former agriculture minister Wagner Rossi – who resigned in 2011 over corruption allegations – as well as the head of the logistics firm which allegedly benefitted from President Temer's decree.
The offices of the firm, called Rodrimar, were searched.
Mr Yunes served as special advisor to President Temer until December 2016 when he resigned to fight what he described as "ignominious accusations" being levelled against him.
He was named by jailed financier Lúcio Funaro as one of the people who administered the alleged bribes for President Temer.
Local media said that Mr Yunes's arrest and that of the other four suspects would increase pressure on Mr Temer, who only last year survived a corruption vote in Congress linked to a separate investigation.
Brazil has in recent years been engulfed in a massive corruption scandal, which has seen dozens of top politicians and business people investigated and some of them jailed.
Former President Lula could be sent to jail next week after he was sentenced last year to 12 years in prison for corruption on charges which he is still appealing against.