Libya's National Transitional Council leader Mustafa Abdel Jalil kneeled in prayer after taking the stand in a celebration of liberation on Sunday after 42 years of one-man rule by Muammar Gaddafi and promised to uphold Islamic law.
"We as a Muslim nation have taken Islamic sharia as the source of legislation, therefore any law that contradicts the principles of Islam is legally nullified," he said.
Jalil thanked the Arab League, the United Nations, and the European Union for supporting the uprising which ended with Gaddafi's death on Thursday.
"All the martyrs, the civilians and the army had waited for this moment. But now they are in the best of places ... eternal heaven," he said, shaking hands with supporters.
"The revolution began as a peaceful one. But it was faced with violence," he told tens of thousands of Libyans gathered in the eastern city of Benghazi, where fighting against Gaddafi erupted in February.