(Adds former President George H. W. Bush) Aug 25 (Reuters) -...

(Adds former President George H. W. Bush)

Aug 25 (Reuters) - John McCain, a former prisoner of war in Vietnam who served as a U.S. senator from Arizona for more than three decades, died on Saturday at the age of 81.

Below are some of the reactions to his death:

SENATE MAJORITY LEADER MITCH MCCONNELL "In an era filled with cynicism about national unity and public service, John McCain's life shone as a bright example. He showed us that boundless patriotism and self-sacrifice are not outdated concepts or cliches, but the building blocks of an extraordinary life."

FORMER PRESIDENT BARACK OBAMA AND MICHELLE OBAMA "Few of us have been tested the way John once was, or required to show the kind of courage that he did. But all of us can aspire to the courage to put the greater good above our own. At John's best, he showed us what that means. And for that, we are all in his debt. Michelle and I send our most heartfelt condolences to Cindy and their family."

FORMER PRESIDENT GEORGE W. BUSH "Some lives are so vivid, it is difficult to imagine them ended. Some voices are so vibrant, it is hard to think of them stilled. John McCain was a man of deep conviction and a patriot of the highest order. He was a public servant in the finest traditions of our country. And to me, he was a friend whom I'll deeply miss."

FORMER VICE PRESIDENT JOE BIDEN "As a POW, John endured the worst of what human beings can do to one another. In politics, he fell short of his greatest ambition. At the end of his life he faced a cruel and relentless disease. And yet through it all he never lost sight of what he believed most: Country First. And the spirit that drove him was never extinguished: we are here to commit ourselves to something bigger than ourselves."

FORMER PRESIDENT JIMMY CARTER "John McCain was a man of honor, a true patriot in the best sense of the word. Americans will be forever grateful for his heroic military service and for his steadfast integrity as a member of the United States Senate."

U.S. VICE PRESIDENT MIKE PENCE "Karen and I send our deepest condolences to Cindy and the entire McCain family on the passing of Senator John McCain. We honor his lifetime of service to this nation in our military and in public life. His family and friends will be in our prayers. God bless John McCain."

FORMER PRESIDENT GEORGE H. W. BUSH "John McCain was a patriot of the highest order, a public servant of rarest courage. Few sacrificed more for, or contributed more to, the welfare of his fellow citizens - and indeed freedom-loving peoples around the world. Another American maverick and warrior, General George Patton, once observed: "We should thank God that men such as these have lived."

ARIZONA GOVERNOR DOUG DUCEY "John McCain is one American who will never be forgotten. He was a giant. An icon. An American hero. But here at home, we were most proud to call him a fellow Arizonan. Like so many of us, he was not born here, but his spirit, service and fierce independence shaped the state with which he became synonymous."

CANADIAN PRIME MINISTER JUSTIN TRUDEAU "Senator John McCain was an American patriot and hero whose sacrifices for his country, and lifetime of public service, were an inspiration to millions. Canadians join Americans tonight in celebrating his life and mourning his passing."

HOUSE MINORITY LEADER NANCY PELOSI "The nation is in tears. Today, with the passing of John McCain, Congress and America have lost a leader and public servant of deep patriotism, outstanding bravery and undaunted spirit."

FORMER GOVERNOR OF ALASKA SARAH PALIN "Today we lost an American original. Sen. John McCain was a maverick and a fighter, never afraid to stand for his beliefs. John never took the easy path in life - and through sacrifice and suffering he inspired others to serve something greater than self."

AUSTRALIAN PRIME MINISTER SCOTT MORRISON "Senator John McCain was a true friend of Australia who was committed to strengthening the alliance between our two nations. He was a man of great courage and conviction. Our thoughts and prayers go out to his wife, Cindy, and all the McCain family during this time."