Sean Penn won the best actor Oscar on Sunday for his portrayal of a trailblazing gay politician in the biopic 'Milk' and made an emotional plea for gay rights.

It was the 48-year-old's second best actor Academy Award following his win for the 2003 drama 'Mystic River'.

"Thank you. Thank you. You commie, homo-loving sons-of-a-gun. I did not expect this," Penn told the awards ceremony.

And in a nod to his bad boy past he added: "I wanted to be very clear that I do know how hard I make it to appreciate me often."

He also made a plea for those who have voted against gay marriage to rethink their positions.

"I think that it is a good time for those who voted for the ban against gay marriage to sit and reflect and anticipate their great shame and the shame in their grandchildren's eyes if they continue that way of support. We've got to have equal rights for everyone," Penn said.

Other nominees for best actor included Mickey Rourke for 'The Wrestler', Richard Jenkins for 'The Visitor', Frank Langella for 'Frost/Nixon' and Brad Pitt for 'The Curious Case of Benjamin Button'.

AFP