A leaked Justice Department memo has revealed the US government's justifications for using drones to kill Americans abroad.

It says citizens can legally be targeted if they're involved in ongoing plots against the United States.

Drone attacks in Pakistan and Yemen have wide backing among American voters but stir very strong feelings in the areas targeted.

Barack Obama has hugely expanded the programme, killing many al-Qaeda suspects but many others too.

He argues it's self-defence, and within international law.

The BBC's Washington Correspondent Jane Little has more.