There is a 'slim' chance that a newly discovered asteroid -- 2003 QQ47 -- may hit Earth on March 21, 2014, British astronomers have said.

2003 QQ47 has a mass of around 2.6 billion tonnes and is 1.2 kilometres wide.

If the asteroid hits our planet, the impact would unleash force of 350,000 megatonnes, which is around eight million times more powerful than the atomic bomb dropped over Hiroshima, Japan in 1945. On impact it would be travelling at 75,000 miles an hour.

The astronomers, who use the Torino scale to rate the chances of newly discovered asteroids and comets hitting the earth, classify the chances of the asteroid hitting the earth as 'an event meriting careful monitoring'.

But they are quick to point out the probability of such a collision was just one in 909,000.

The asteroid is around one-tenth of the size of the meteor that is believed to have wiped out dinosaurs on Earth 65 million years ago, said Kevin Yates, project manager of the near-Earth object information centre in Leicestershire central England.

"As additional observations are made over the coming months, and the uncertainties decrease, asteroid 2003 QQ47 is likely to drop down the Torino scale," Yates added.