8:05 PM PT -- Just a couple hours before Diddy got busted, he was confidently strolling around NYC with his son Christian "King" Combs. He even stopped to greet some fans and take selfies.

7:13 PM PT -- A law enforcement source tells TMZ ... Diddy's arrest was scheduled for Tuesday. But something happened that caused the feds to move in a day earlier.

However, U.S. Attorney Damian Williams says federal agents took him in based on a sealed indictment filed by the Southern District of New York.

Diddy was just arrested and taken into federal custody in New York Monday night ... TMZ has learned.

Sources tell TMZ ... Homeland Security swooped into a midtown hotel late Monday where Diddy was staying and they arrested him. We have unconfirmed reports the feds are searching his hotel room.

We're told Diddy was taken to the federal building in lower Manhattan.

It appears the action was taken in connection with the ongoing criminal investigation into alleged sex trafficking and other offenses that led to search warrants being issued and executed at Diddy's homes in Beverly Hills and Miami. As we reported, a grand jury has been hearing testimony from various accusers over the last few months.

Diddy's attorney, Marc Agnifilo, tells TMZ, "We are disappointed with the decision to pursue what we believe is an unjust prosecution of Mr. Combs by the U.S. Attorney’s Office. Sean “Diddy” Combs is a music icon, self-made entrepreneur, loving family man, and proven philanthropist who has spent the last 30 years building an empire, adoring his children, and working to uplift the Black community."

Agnifilo adds, "He is an imperfect person but is not criminal. To his credit Mr. Combs has been nothing but cooperative with this investigation and he voluntarily relocated to New York last week in anticipation of these charges. Please reserve your judgment until you have all the facts. These are the acts of an innocent man with nothing to hide, and he looks forward to clearing his name in court."