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Justin Bieber fans have a message for Kim Kardashian: Back off!

After she mingled with the teen idol Saturday at the White House Correspondents' dinner in Washington, D.C., she Twittered that she had "Bieber fever."

He quickly replied, calling her his "girlfriend."

Now, the E! reality star, 29, has Twittered, "I'm getting death threats from your fans! This is unBeliebable!!!"

Bieber, 16, is shocked. "Seriously?" he responded.

Bieber fans have been going bananas lately.

Last month, his mother was trampled on by a herd of about 500 waiting to greet him as he arrived in New Zealand. He was forced to issue the following statement to them: "Let's keep it safe and have fun."

Bieber also recently scrapped a show in Sydney, Australia, after a crowd of about 5,000 teenage girls got rowdy, causing minor injuries to eight of his fans in addition to others fainting.

In March, Bieber's album My World 2.0 soared to the No. 1 spot on the Billboard charts within a week of its release.