Thousands of mourners gathered in central Beirut on Sunday for the funeral of slain internal security chief Wissam al-Hassan, a ceremony likely to become a rally against Syrian authorities. General al-Hassan, a prominent figure opposed to Syrian President Bashar al-Assad, died when a powerful bomb exploded in an upmarket Beirut suburb on Friday, sparking angry calls for Prime Minister Najib Mikati and his government to quit. The slain police intelligence chief is to be buried late afternoon in Beirut alongside the grave of his mentor, former Prime Minister Rafiq Hariri, whose 2005 assassination sparked an outcry that forced Syrian troops to withdraw from Lebanon after three decades of occupation. Lebanese politicians have accused Syria's leadership of having a role in the assassination, which deepened fears the civil war there is spreading beyond its borders. Soldiers deployed in force across Beirut in preparation for the funeral, with squads standing guard at road junctions and stopping cars from entering the downtown area. A mosque in central Martyrs' Square, where Hassan is due to be buried, broadcast prayers for the dead early on Sunday. Protesters had blocked roads with burning tyres and gunmen took to the streets of Beirut and Tripoli on Saturday. In the evening small groups of protesters waving Lebanese flags marched to the government offices. But the city was otherwise quiet overnight as residents stayed at home fearing more violence and jeeps loaded with soldiers cruised the streets. Even the night-life areas of Hamra and Gemmayzeh were subdued, with many restaurants closed. Former prime minister Saad al-Hariri accused Syrian President Bashar al-Assad of being behind the bombing and Lebanon's political opposition demanded the resignation of Prime Minister Najib Mikati, whose government includes Syria's Shi'ite Muslim ally Hezbollah. The death of Hassan, a Sunni Muslim from the northern city of Tripoli who was close to the powerful Hariri political clan, has inflamed Sunni anger.