American Serena Williams has been knocked out of the 2012 Australian Open, in a shock upset by the unseeded Ekaterina Makarova.

The 2010 winner of the tournament made 37 unforced errors as the 56th-ranked Makarova won 6-2, 6-3 in 82 minutes. The result ended Williams' 17-match Australian Open-winning streak. Her last defeat in Melbourne came in the quarterfinals against Serbian Jelena Jankovic in 2008.

I don't know what to say. It's an amazing feeling, said Makarova, the 23-year-old Russian left-hander. She's an unbelievable player. It's really tough to play against her so I'm really happy I finished it, she added.

The 30-year-old Williams, seeded 12th, saved five set points before dropping the opening set and three match points on her serve in the final game.

I can't even describe how I served to be honest, it wasn't good though, Williams said.

Meanwhile, Makarova will meet the winner of the match between Maria Sharapova and Sabine Lisicki, in the quarter-finals. This is her first quarter-final appearance at a Grand Slam.

Check out photographs of the match here...