AN asteroid the size of an Olympic swimming pool has had a close shave with Earth, racing past at a distance of just 17,200 miles.

The 50-metre-wide space rock – dubbed a "city killer" because it would be capable of crushing an average metropolis on impact – came closer to the planet than any other object of a similar size ever has.

Its closest approach was at 7.25pm, when it came even closer than the satellites that orbit earth, but scientists said there was no risk of an actual collision.

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The asteroid's arrival was preceded by a damaging meteor event in Russia on Friday, but indications from the meteor's path suggest the two events are entirely unrelated.

The asteroid, named 2012 DA14, was first spotted in February by astronomers at the once small-scale and amateur La Sagra Sky Survey in Spain.

It has in recent years become a significant contributor to our knowledge of these "near-Earth objects".