The attack that killed at least 41 people in the Lebanese capital, Beirut, reveals a shocking disregard for human life, said Amnesty International.
“This was a gruesome and unjustifiable suicide attack in a populated civilian area,” said Philip Luther, Director of the Middle East and North Africa Programme at Amnesty International.
“The Lebanese authorities must ensure that those responsible for this terrible crime do not go unpunished.”
This attack also highlights the growing risk of contagion from the Syrian conflict.
“Until all sides responsible for the countless war crimes and crimes against humanity in the conflict in neighbouring Syria are brought to account, the violence will continue to pose a menace beyond Syria’s borders,” Philip Luther said.
“We again call on the UN Security Council to refer the situation in Syria to the International Criminal Court, so that all suspected war crimes and crimes against humanity can be investigated.”
Thursday’s attack was among the deadliest in Beirut since the end of the Lebanese civil war in 1990.
The armed group that calls itself Islamic State (IS) says it was responsible for the attack, in which two suicide bombers blew themselves up in the predominantly Shi’a suburb of Burj al-Barajneh.
Predominantly Shi’a fighters from the military wing of Lebanon’s Hizbullah have been supporting Syrian government forces in neighbouring Syria in their fight against other armed groups, including IS.