Federal Bureau of Investigation agents carrying court-authorised search warrants have seized documents from US President Donald Trump's personal lawyer Michael Cohen.

That's according to a statement from Cohen's lawyer, Stephen Ryan. He says the search warrants were executed by the office of the US Attorney for Southern District of New York but they are "in part" related to Special Counsel Robert Mueller's investigation.

Cohen is Trump's longtime personal lawyer. He has been under heavy public scrutiny in recent months for his payment of US$130,000 to porn star Stormy Daniels, who claims to have had an affair with Trump in the mid-2000s.

Ryan says agents seized "protected attorney client communications." He is not elaborating on the contents.


Ryan called the tactics "inappropriate and unnecessary," saying Cohen has "cooperated completely with all government entities, including providing thousands of non-privileged documents to the Congress and sitting for depositions under oath."

- AP, Washington Post