Lady Gaga joined Sting and Sir Elton John onstage at a star-studded charity fundraiser in New York last night (May 13).

The singer, who was wearing a bizarre 'warrior mask', was mobbed by fans as she left Carnegie Hall following the Rainforest Fund benefit.

Earlier, Lady Gaga had wowed fans when she took to the stage alongside Sting to perform ‘Stand By Me Together’.

The pair were joined later in the evening by Sir Elton John, Dame Shirley Bassey and Debbie Harry on a cover of Journey’s ‘Don’t Stop Believin’’.

Lady Gaga was embraced by Sir Elton during the performance, while Springsteen and Dame Shirley also shared a microphone.

The event was held to mark the 21st anniversary of the Rainforest Fund, which was setup by Sting and wife Trudie Styler to help protect endangered rainforests across the globe.

Lady Gaga halted her European tour to return to the US especially for the concert.

(by Jason Gregory)