The week in pictures: 9/11 anniversary, far-right win in Germany and Houthis' Yemen offensive

A look back at some of the week's key news stories and the most striking images, from commemorations marking 25 years since the 9/11 attacks to the breakthrough win for Germany's far-right AfD party and the lightening offensive that has left Yemen's Iran-backed Houthi rebels in control of the country's Red Sea coast.