Sri Lankan Prime Minister Ranil Wickremesinghe on Monday offered his condolences to UN Secretary General Antonio Guterres over the passing away of former UN chief Kofi Annan last week.

In a letter sent to Guterres, Wickremesinghe said Annan served the United Nations with distinction and calling himself an eternal optimist, he devoted his entire life to working towards peace among nations, peoples and communities.

Annan also achieved the noble goals of the United Nations towards achieving better living conditions and a fairer and just world for all, Wickremesinghe said.

"We all recall with much gratitude, His Excellency Kofi Annan's visit to Sri Lanka following the devastation caused by the December 2005 Tsunami. His compassion, sense of empathy and calm demeanor soothed many who were grieving and in pain," he said.

"Similarly, the work he carried out throughout his life brought peace and comfort to many around the world," the prime minister added.

Wickremesinghe further said that while Annan will forever remain in the hearts of the people that he touched, his memory will continue to inspire and guide everyone to continue their journey of working for peace, justice, democracy, rule of law and human rights for all.

Annan, who served as UN secretary-general from January 1997 to December 2006, passed away on Saturday at the age of 80.