Four former Lebanese security chiefs known for their pro-Syrian stance have been arrested.They are being treated as ‘suspects’ in the assassination of former Lebanese prime minister Rafik al-Hariri in February, according to officials. Their detention is in connection with the UN-investigation into the killing. Hariri’s death plunged Lebanon into political turmoil, with mass demonstrations against Syrian influence in the country. Damascus denied involvement in the bomb blast, but bowed to international pressure and withdrew its troops from Lebanon in April. Supporters of Hariri have repeatedly accused the men arrested of some involvement in his killing, but have not presented firm proof.