Rights groups Amnesty International and Human Rights Watch urged the United Nations on Tuesday to refer the conflict in Syria to the International Criminal Court.
The statements came after a report by UN chemical weapons inspectors confirmed that sarin gas sarin was used in attacks on the outskirts of Damascus on August 21.
Under a Russian-led deal, Syria has agreed to give up its chemical arsenal, but the groups warned that the deal must not allow war crimes to go unpunished.
"Crimes under international law are being perpetrated on a daily basis in Syria. Accountability for the 21 August attacks and other violations are long overdue," Amnesty said.
It urged the UN Security Council "to refer the situation in Syria to the International Criminal Court and to insist that the Syrian government grants cross-border access, as well as cross-line access, to humanitarian aid."
Richard Dicker, Human Rights Watch's international justice director, said referring the conflict to the ICC was "essential for justice."
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"To lock up the chemical weapons and not prosecute those who used them is an affront to the civilians who died," he said.
"Referring Syria to the ICC is essential for justice for the tens of thousands of civilians killed in Syria by all sides since the conflict there began," he added.
Security Council members are trying to draw up a resolution on the Syrian chemical weapons disarmament deal, but there are disagreements about whether it will allow the use of force for implementation of the agreement and if it will include an ICC referral.
HRW noted that both the Syrian regime and the rebels fighting against it are accused of committing abuses in the conflict that began in March 2011.
"An ICC referral would send a strong message to all parties to the conflict in Syria that grave crimes in violation of international law -- including war crimes and crimes against humanity -- will not be tolerated," HRW said.
At least 110,000 people have been killed in the Syrian conflict, according to a monitoring group.
Reports suggest hundreds were killed in the August 21 attack, which the opposition blames on the regime, though the government denies responsibility.