The US attorney general has acknowledged four US citizens were killed in drone strikes since 2011. The US specifically targeted and killed Anwar al-Awlaki, Eric Holder wrote in a letter to the Senate judiciary panel. Awlaki's 16-year-old son Abdulrahman, Samir Khan and Jude Mohammad were "not specifically targeted by the US". The disclosure of the killings in Yemen and Pakistan marks the first formal public acknowledgement of the US citizen deaths in drone strikes. "The president has directed me to disclose certain information that until now has been properly classified," Mr Holder wrote. 'Continuing threat' America's top law enforcement official...