UN Secretary-General Ban Ki-moon said Thursday that the death of Libya's fallen leader Muammar Gaddafi and the end of fighting in the North African country "marks a historic transition of Libya," adding that the death of Col. Gaddafi is "only the end of the beginning."

He also called upon the pro-Gaddafi fighters to "lay down their arms in a peace."

"Clearly, this day marks a historic transition for Libya," said the secretary-general at an interactive dialogue on global sustainability, which was organized by the UN General Assembly.

"In the coming days we will witness scenes of celebration as well as grief for those who lost so much," Ban said. "Yet let us recognize immediately that this is only the end of the beginning -- the road ahead for Libya and its people will be difficult and full of challenges."

Ban took the opportunity to make the statement on the latest development in Libya after reports said Gaddafi was dead and the fighting in Sirte, Gaddafi's hometown, and other cities in Libya, has come to an end.