Sandy Hook survivors sing at Super Bowl

Surviving students from the Sandy Hook Elementary School shooting have given an emotional performance at the Super Bowl.

Twenty six children sang America the Beautiful to honour the 20 first-graders and six adults who were killed in the December 14 Newtown massacre.

Jennifer Hudson join the student chorus.

The Sandy Hook tearjerker was followed by Alicia Keys' rendition of The Star Spangled Banner.

Keys performed a loungey, piano-tinged - and live - version of the national anthem ahead of the NRL extravaganza.

The Grammy-winning singer played the piano as she sang The Star Spangled Banner with her eyes shut.

Her publicist said the performance was live, days after halftime performer Beyonce admitted singing along to a pre-recorded track at the presidential inauguration.

Keys' version was soft and featured additional lyrics: She added "living in the home" before belting "home of the brave" as she finished the song.

Beyonce brought some female spirit to the football stage in a dance-heavy, 13-minute half-time performance.

She sang live, too, with her background singers helping as the pop star danced around the stage.

She emerged onstage singing some of Love on Top, transitioning to her hit Crazy In Love in an all-black ensemble. She ripped off part of her shirt and skirt as she danced hard with background dancers doing the same.

Her Destiny's Child band mates joined her for their hits Bootylicious and Independent Woman, but Kelly Rowland and Michelle Williams were barely heard. They also jumped in for some of Single Ladies (Put a Ring On It), where Beyonce's voice got better.

She sounded best on Halo, which she belted on a bended knee.

A power failure early disrupted the third quarter of the National Football League's title game between the Baltimore Ravens and the San Francisco 49ers

Players from both teams retreated to the sidelines as the public-address announcer cautioned fans to remain in their seats. Fans amused themselves by doing the wave.