Amanda Bynes has caused outrage by sending Rihanna a series of shocking and racist tweets.

The troubled star - who was charged with attempted evidence tampering, reckless endangerment and marijuana possession in court on Friday (05.24.13) - took to social networking site Twitter to slam the 25-year-old superstar, notably suggesting her on/off boyfriend Chris Brown beat her up in 2009 because she wasn't ''pretty enough''.

She wrote: ''@Rihanna you look so ugly tryin to be white (sic)'', before adding, ''Chris Brown beat you because you're not pretty enough.''

The 'She's The Man' actress then retweeted a post from Rihanna which read, ''Look who came to see me!! My lover Stella Mccartney!!!'', adding, ''No one wants to be your lover so you call everyone and their mother that I almost named my new dog Rihanna.''

Rihanna remained unfazed by the unprovoked insults and poked fun of Amanda's fragile state of mind, joking she would have been a perfect contestant on former reality show 'Intervention'.

She posted: ''Ya see what happens when they cancel Intervention?''

A furious Amanda snapped back: ''Unlike ur fugly faced self I don't do drugs! U need the intervention dog! I met ur ugly face in person! U aren't pretty u know it! (sic)''

The bizarre tweets have since been deleted. The outburst comes after a difficult week for the former child star, who was arrested in her New York City apartment after being discovered smoking marijuana and behaving erratically in the lobby.

Amanda has since accused her arresting officer of sexually harassing her, a claim which the New York Police Department's Internal Affairs Bureau is looking into.

During yet another Twitter rant on Saturday (05.25.16), the 27-year-old actress alleged an officer entered her apartment illegally, touched her inappropriately and lied about her throwing a bong out the window in front of him.