PARIS (Reuters) - Senior French conservatives and Socialist presidential candidate Benoit Hamon said on Sunday that they would back centrist Emmanuel Macron in a May 7 runoff against far-right leader Marine Le Pen.

After initial projections indicated Macron and Le Pen had qualified for the second round, Socialist candidate Benoit Hamon told supporters his party had suffered an "historic blow" from its voter base and called on voters to back Macron and reject Le Pen in "the strongest possible way".

On the other side of the traditional political spectrum, former prime minister Jean-Pierre Raffarin, a member of defeated candidate Francois Fillon's The Republicans party, said: "Without hesitation, as far as I'm concerned we've got to rally behind Emmanuel Macron."

(Reporting by Ingrid Melander, Michel Rose, Bate Felix, John Irish; writing by Leigh Thomas, editing by Andrew Callus)