Shia pilgrims gather in Karbala amid security fears

Hundreds of thousands of Shia pilgrims have converged on the holy city of Karbala in Iraq, for one of their most important annual gatherings - the birth anniversary of imam al-Mehdi 12 centuries ago. But with the country in the middle of a political crisis, many fear their security can't be guaranteed. Al Jazeera's Jane Arraf reports.