A senior astronomer has said that the hunt for alien life should take into account alien "sentient machines".

Seti, the Search for Extraterrestrial Intelligence, has until now sought radio signals from worlds like Earth.

But Seti astronomer Seth Shostak argues that the time between aliens developing radio technology and artificial intelligence (AI) would be short.

Writing in Acta Astronautica, he says that the odds favour detecting such alien AI rather than "biological" life.

Alien hunters 'should look for artificial intelligence'