10/7 8:30 AM PT -- As of Sunday morning, Katt remained in a Portland jail. Law enforcement sources tell us they have to wait until Monday to decide whether Katt will be extradited to Georgia where he faces a felony warrant.

3:40 PM PT -- Katt allegedly attacked the driver of a town car that was supposed to take him to the Moda Center Friday night after an argument about transporting his dog ... according to the police report.

Cops say the driver sustained minor injuries to the face -- including swelling and cuts -- and was treated at a local hospital. Katt left the scene of the alleged assault in another vehicle.

According to the report ... cops located Katt Saturday morning to investigate the incident and arrested him. They also discovered he had an out-of-state warrant.

Katt Williams has been arrested for alleged assault in Portland, Oregon.

The comedian was arrested by Port of Portland police and booked for misdemeanor assault Saturday. His bail's been set at $2,500.

As of now ... it's unclear what Williams did to get arrested, but the Multnomah County Sheriff's Office lists him as a fugitive in another jurisdiction. We're told he may be sent to Atlanta, which could possibly be related to this fugitive status.

Katt was supposed to be a part of Nick Cannon's 'Wild 'N Out Live' concert at the Moda Center Friday night in Portland. We're told he was at the venue at some point, but never made the show.