Troops loyal to Ali Abdullah Saleh, the Yemeni president, have opened fire on protesters in Sanaa, killing at least 15 people and injuring hundreds.<br /><br />Tens of thousands of protestors calling for an end to president Saleh's 33-year rule took to the streets of the capital a day after protesters stormed Yemen's main university.<br /><br />Al Jazeera's Imran Khan reports.
