Lebanese authorities arrested one Palestinian and five Syrian suspects on Saturday in connection with Thursday's twin suicide bombings in central Beirut, which killed 43 and injured more than 200, a senior security source told Reuters.

The bombings, claimed by Islamic State, took place in a stronghold of the Lebanese Shi'ite movement Hezbollah. Lebanon's Hezbollah leader Sayyed Hassan Nasrallah said Syrian and Lebanese suspects were arrested on charges of being involved in the attacks. He did not mention if one of them was a Palestinian.

The explosions were the first in more than a year to target a Hezbollah stronghold in Lebanon. On Saturday, the country held a day of mourning, with the attacks declared as one the nation's biggest tragedies ever. Since Russia launched air strikes in support of Syrian president Bashar al-Assad on September 30, Hezbollah has sent hundreds of fighters to buttress his fight against insurgents, including the Islamic State.