Four top Scottish universities have dropped down the rankings of the international league table.

The QS World University Rankings 2018 released on Thursday show that the four remain among the top 200 in the world but have fallen down from the positions they held in the table last year.

Edinburgh University is the highest ranking Scottish institution, but it has dropped out of the world's top 20 to sit at 23, down from 19 last year.

Glasgow University fell two places from 63 to 65, while the oldest university in Scotland, St Andrews, fell 15 places and now sits at 92.

Aberdeen University is down 17 places from 141 to 158 this year.

The Massachusetts Institute of Technology (MIT) was named the top university in the world, while Cambridge University was the highest ranking UK institution as it was in at number five, one place ahead of Oxford University.