Thomas, centre, was considered the dean of White House correspondents (REUTERS)

Born in the US city of Detroit in 1920, Helen Thomas is regarded as a pioneer for women in journalism. 

Thomas, a tough interrogator, worked for the United Press Internatoinal news agency from 1943 before moving to Hearst Newspapers in 2000 as a columnist.

She covered many beats typically concerning the federal government in her early years with United Press Internatoinal, before joining the agency's White House team after John F Kennedy was elected to office in the 1960s, becoming a White House correspondent.

She travelled many times with presidents, including Richard Nixon, Ronald Reagan and Bill Clinton, on foreign trips. In 1972 she accompanied Nixon on his historic visit to communist China during the Cold War.

Thomas repeatedly grilled George Bush and his administration over the 2003 Iraq war and subsequent occupation.

She was the first female office bearer and then president of the White House Correspondents' Association.

Considered the dean of White House correspondents, Thomas had a seat reserved for her in the building's press briefing room, on the front row.