Who is behind the crisis in Yemen? Frank Gardner explains

The conflict between the Houthi rebels in Yemen and forces loyal to President Abdrabbuh Mansour Hadi has pushed the country "to the edge of civil war", according to the UN's special adviser.

It has also widened into a broader conflict, with Saudi Arabia launching air strikes against the Houthis. Iran has decried the action as "genocide" and responded by moving naval ships towards the Yemeni coast.

The disruption has also allowed al-Qaeda in the Arabian Peninsula (AQAP) to take control in parts of the country.