Democrat Tom Lantos, a key voice in Congress on US foreign affairs died on Monday.

Lantos' representatives say he was surrounded by his family when he died Monday morning in Bethesda naval hospital north of Washington.

Lantos served as representative from California since 1980. He also chaired the chamber's Foreign Affairs committee.

When he announced his diagnosis, Lantos, expressed his "profoundly felt gratitude to this great country."

"It is only in the United States that a penniless survivor of the Holocaust and a fighter in the anti-Nazi underground could have received an education, raised a family, and had the privilege of serving the last three decades of his life as a member of Congress," he said.

Tributes quickly poured in for Lantos, from across the political aisle.

President George W. Bush hailed him as a "champion" of human rights.

"As the only Holocaust survivor to serve in Congress, Tom was a living reminder that we must never turn a blind eye to the suffering of the innocent at the hands of evil men," Bush said in a statement issued from the White House, where flags were lowered to half-staff.

Hillary and Bill Clinton remembered the "courageous and improbable journey" of Lantos's life.

"Tom bore witness to the worst of human cruelty and devoted his life to stopping it," the Clintons said in a statement.

Congressman Lantos had just turned 80 years old.