Jordan on Monday sentenced four people to two years in jail each for having tried to join the ranks of the Islamic State group and for promoting the jihadists online. The kingdom is one of five Arab nations that joined a US-led air campaign against the Sunni extremist group that has declared a "caliphate" straddling the borders of neighbouring Iraq and Syria. Since the start of the campaign in September 2014, Jordan has reportedly arrested dozens of suspected IS sympathisers and put several on trial.