Lebanese soldiers have fired bullets in the air and launched tear-gas at mourners attending the funeral of a murdered intelligence chief in Beirut amid concerns that violence from the Syrian civil war is spilling over the border.
Security forces clashed with protestors, angry at what they believe to be Syria's role in the murder, after they tried to storm a government office demanding the resignation of Prime Minister Najib Mikati.
Opposition leader Saad al-Hariri urged supporters to end the violence.
"We want peace, the government should fall but we want that in a peaceful way. I call on all those who are in the streets to pull back," he said.
Hassan had recently helped to bring about the arrest of one of Syria's top allies in Lebanon on suspicion of planning to carry out terrorist attacks.
Hassan was also leading an investigation into the assassination of Lebanese Prime Minister, Rafik Hariri, in 2005, an event widely believed to have been the work of Syria and its Lebanese ally, Hezbollah.
The Lebanese opposition have accused Mikati's government of being too close to President Bashar al-Assad's Syrian regime.
Lebanon is deeply divided between Shias who generally support al-Assad and Sunnis who oppose him.
The influential Shia militant group, Hezbollah, holds 14 seats in the Lebanese parliament and receives funding from Syria as well as Iran.
There are fears that Syria's civil war could spill over borders in the highly volatile region.
Lebanon has long been dependent on the whims of its much larger neighbour and could find itself being drawn into the conflict as deep-rooted sectarian tensions are inflamed by the violence.
Lebanon fought its own civil war from 1975-90 during which time Syria stationed troops in the country. Despite the war ending in 1990, Syrian troops remained until the assassination of Hariri.