WASHINGTON, Aug. 26 (Xinhua) -- World leaders on Wednesday paid tribute to and mourned the passing of U.S. Senator Edward Kennedy, who died at 77 after a yearlong struggle with brain cancer.
Edward Kennedy, nicknamed "Teddy", was the brother of former U.S. President John Kennedy who was assassinated in 1963. He was the last of Kennedy brothers in the legendary family and known as "The Lion of the Senate."
Upon learning Kennedy's death, UN Secretary-General Ban Ki-moon extended "deep sympathies" to Kennedy's family and spoke highly of Kennedy's strong and firm support for "so many of the principles of the United Nations."
"He was not just a friend of those of power and high position, but even more to those who had neither," Ban said in a statement. "He was a voice for those who would otherwise go unheard, a defender of the rights and interests of the defenseless."
UN High Commissioner for Refugees Antonio Guterres said the life of the late senator and brother of former U.S. President John F. Kennedy is a testimony to the difference a single policy-maker can make.
The UN refugee chief praised Kennedy for keeping "the plight of refugees on the international and national agenda," and "promoting policies and laws that saved and shaped countless lives."
For nearly five decades in the U.S. Senate, Kennedy fought for legislation improving the treatment of refugees and asylum-seekers and reducing discrimination against them.
Three hours after Kennedy died, U.S. President Barack Obama, who was on a vacation in an East Coast resort, said his family was "heartbroken" at the news.
"An important chapter in our history has come to an end," Obama said in a statement. "Our country has lost a great leader, who picked up the torch of his fallen brothers and became the greatest United States Senator of our time."
"For five decades, virtually every major piece of legislation to advance the civil rights, health and economic well-being of the American people bore his name and resulted from his efforts," the statement said.
Kennedy was one of the politicians who endorsed Obama, the then first-term senator from Illinois, in the early phase of the presidential campaign in 2008, and he presented himself several times at Obama's rallies.
Obama ordered that the flag of the United States shall be flown at half-staff at the White House and upon all public buildings and grounds to mourn the Massachusetts senator.
Some former U.S. presidents also joined in mourning him.
Jimmy Carter, who beat Kennedy in the 1980 Democratic presidential nomination, called his old rival "an unwavering advocate for the millions of less fortunate in our country."
Former President George H. W. Bush issued a statement on behalf of himself and his son, former President George W. Bush, expressing sympathies from members of the Republican Party.
"Kennedy was a seminal figure in the U.S. Senate -- a leader who answered the call to duty for some 47 years, and whose death closes a remarkable chapter in that body's history," Bush said.
In Britain, where Kennedy received an honorary knighthood from the Queen in March for his services to the U.S.-British relationship and to the Northern Ireland peace process, Prime Minister Gordon Brown said Kennedy "will be mourned not just in America but in every continent."
Crowning him the "Senator of Senators", Brown said that he was proud to have counted him as a friend.
In Germany, Chancellor Angela Merkel said "Germany and Europe have lost a good and treasured friend."
She lauded Kennedy's "convictions and steadfastness" in advocating justice and peace, saying he was "one of the most prominent politician in American history."
In South Africa, President Jacob Zuma said Kennedy was "a comrade and a friend" of his country "in the fight for liberation."
"We grieve the loss of this great man but the legacy of his contribution to this world will continue to serve as a sort of hope to us," Zuma said in a statement.
Kennedy will be buried at Arlington National Cemetery in Virginia on Saturday, being laid to rest next to President John F. Kennedy and Senator Robert Kennedy.
His death came just weeks after that of his sister Eunice Kennedy Shriver, founder of the Special Olympics, on Aug. 11.