Kofi Annan, the first black African UN secretary-general, died Saturday after becoming ill. After his death was announced, leaders around the world remembered his impact on global politics.

Annan served two terms from Jan. 1, 1997, to Dec. 31, 2006, capped nearly mid-way when he and the U.N. were jointly awarded the Nobel Peace Prize in 2001. Annan was known to diplomats as a lifer — a career diplomat at the United Nations who remained active after his two terms.

The U.N.'s current secretary-general, Antonio Guterres, issued a statement Saturday calling Anna a "force for good."

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"It is with profound sadness that I learned of his passing. In many ways, Kofi Annan was the United Nations. He rose through the ranks to lead the organization into the new millennium with matchless dignity and determination," he said, calling Annan a good friend and mentor.

"He was someone I could always turn to for wisdom and wisdom — and I know I was not alone. He provided people everywhere with a space for dialogue, a place for problem-solving and a path to a better world."

In a statement, former President Barack Obama said Annan embodied the U.N.'s mission like few others.

"His integrity, persistence, optimism, and sense of our common humanity always informed his outreach to the community of nations," he said. "Long after he had broken barriers, Kofi never stopped his pursuit of a better world, and made time to motivate and inspire the next generation of leaders. Michelle and I offer our condolences to his family and many loved ones."

Nikki Haley, the American ambassador to the U.N., said Annan "devoted his life to making the world a more peaceful place through his compassion and dedication to service."

"He worked tirelessly to unite us and never stopped fighting for the dignity of every‎ person," Haley said in a statement. "We join the entire United Nations and diplomatic community in celebrating his life and lifting the Annan family up in love and prayers."

President Nana Akufo-Addo of Ghana called Annan one of the country's "greatest compatriots" on Twitter and said the nation's flag would fly at half-mast throughout the country.

"I extend, on behalf of the entire Ghanaian nation, our sincere, heartfelt condolences to his beloved widow, Nane Maria, and to his devoted children, Ama, Kojo and Nina, on this great loss," Akufo-Addo tweeted. "Rest in perfect peace, Kofi. You have earned it."

Annan was born in the Ashanti heartland two decades before Ghana became the first country in sub-Saharan Africa to gain independence from colonial rule.

South Africa's President Cyril Ramaphosa called Annan a "diplomat extraordinaire."

A diplomat extraordinaire, we will remember Mr @KofiAnnan for his commitment, his leadership and his tireless efforts to advance the African agenda. Our thoughts are with his wife, Nane, his family and loved ones during this difficult time. — President Cyril Ramaphosa (@CyrilRamaphosa) August 18, 2018

German Chancellor Angela Merkel said Annan "inspired me and many others with his ideas, his firm convictions and, not least, his charisma."

She said in a statement that Annan shaped the United Nations "like hardly anyone before him" and said that "he knew how to spark enthusiasm, particularly among young people."

European Commission President Jean-Claude Juncker said in a separate statement he is mourning the "passing of my old friend and inspiration."

"The greatest recognition we can give Kofi Annan is to keep his legacy and his spirit alive. It has never been more important than in today's world," he said.

Other reactions poured in from around the world:

"In a world now filled with leaders who are anything but that, our loss, the world's loss, becomes even more painful." - U.N. human rights chief Zeid Ra'ad al-Hussein

"I sincerely admired his wisdom and courage as well as his ability to make balanced decisions even under the most dire and critical circumstances." - Russian President Vladimir Putin

"A relentless champion for peace and a passionate ambassador for Sesame Street and the world's children." - Sesame Street

"We are devastated ... Africa and the world has lost a special human being." - Nelson Mandela Foundation

"A towering global leader and an unwavering champion for peace, justice and rule of law." - Iranian Foreign Minister Mohammad Javad Zarif

"The U.N. and the world have lost one of their giants." - NATO Secretary-General Jens Stoltenberg

"We give great thanks to God for Kofi Annan, an outstanding human being who represented our continent and the world with enormous graciousness, integrity and distinction." - Former South African archbishop Desmond Tutu

Pamela Falk contributed to this report.