Some of the heaviest fighting in Syria is taking place in and around Qusayr. The rebel offensive to recapture the outskirts of Qusayr is now in its third week, with fierce clashes continue with Hezbollah-backed regime forces. Thousands of residents remain trapped in the city, but the Syrian government says humanitarian workers can only enter once the fighting is over. Al Jazeera's Nadim Baba reports.