Saudi Arabia and Iran trade accusations against a backdrop of sectarian strife

The last few weeks has seen a marked escalation in Saudi-Iranian tension. Regionally the two powers are facing off in Syria, while Riyadh has accused Iran of meddling in its eastern region. The US has revealed dramatic details of a plot to kill the Saudi ambassador in Washington Adel Al-Jubair (see box, below), once again pointing the finger at Iran. But is it just a war of words and accusations, or is there more at play?