Heroes stunner Hayden Panettiere 'threatened to kill' a reporter on the red carpet at the Emmy Awards on Sunday, according to reports.

The 18-year-old allegedly threatened an US Weekly reporter, who ran a story claiming that she had broken up with on/off again boyfriend Stephen Colletti.

According to a TV Guide reporter who was witness to the face-off: “It was the unbreakable Hayden Panettiere who threatened to "kill" a staffer from Us Weekly over something she wrote about her in a recent issue.

”Just when it looked like Hayden was about to pull a Sylar on said reporter's skull, her quick-thinking publicist grabbed her and scolded, "Not on the red carpet." It was a classic Hollywood moment.”

Gossip reports were flying at the beginning of the week of a potential off-screen romance for Panettiere and her Heroes costar Milo Ventimiglia.

The pair were spotted getting ‘cosy’ at the Emmy Awards Governor's Ball on Sunday and were later photographed leaving the event together.