Gainesville, Florida - Bob Graham, former US senator and two-term Democratic governor of the state of Florida, has died aged 87, his family announced Tuesday.

Graham held elected office for almost four decades, beginning as a Florida state representative in 1966 until 2005 when he retired from the US Senate after his third term in office.

He "devoted his life to the betterment of the world around him," said a statement by the family, posted on his daughter Gwen Graham's X account.

"The memorials to that devotion are everywhere – from the Everglades and other natural treasure he was determined to preserve... the global understanding he helped to foster through his work with the intelligence community, and so many more."

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Graham served from 1979 to 1987 as governor of Florida, during which the southern US state experienced a large wave of immigration from Cuba and Haiti.

As the chair of the Senate Intelligence Committee after the September 11, 2001 attacks, Graham led a joint congressional inquiry into the US government failures leading up to the events.

He later strongly opposed then-president George W. Bush's push to invade Iraq and topple Saddam Hussein, arguing that resources would be diverted from the fight against terrorism.

"It was with the deepest respect and sadness that I learned of the passing of Senator Bob Graham: a patriotic American and a great Member of the United States Senate," said former US House Speaker Nancy Pelosi.

Several years after leaving the Senate, Graham was tapped by former president Barack Obama to co-chair an inquiry into the major Deepwater Horizon oil spill in the Gulf of Mexico.