Justin Bieber's rapper friend Lil Twist has been accused of attacking a woman during a party at the pop star's Calabasas, California mansion, according to reports.

The accuser alleges Lil Twist, whose real name is Christopher Moore, grabbed her by the arm and tried to prevent her from leaving the bash early on Thursday (01Aug13), according to Tmz.com.

The unnamed woman went straight to the nearby sheriff's department to report the matter and police are investigating the claims, the website reports.

The latest legal issue comes just weeks after the rapper was arrested on suspicion of Dui, while driving Bieber's Fisker Karma sportscar, and in March (13), Moore crashed the same car into cement poles in a San Fernando Valley, California parking lot.

Bieber was not at home during the party at the centre of the new legal dispute.