Spanish military authorities placed 100 junior officers and soldiers under two weeks' house arrest today after they signed a statement attacking government and press treatment of the armed forces.

The Defense Ministry ordered an investigation into the document, which expressed sympathy with the officers indicted in connection with a coup attempt in February and pointed to continued restiveness in the Army.

The statement, signed by captains and sergeants garrisoned here, appeared to signal a confrontation between civilian powers and sectors of the Army. An editorial by the Madrid independent daily El Pais termed the statement "inadmissible and provocative."

Publication of the statement was timed to coincide with official celebrations today of the third anniversary of a national referendum that endorsed a democratic constitution to replace the Francoist dictatorship.

Senior government ministers interrupted their weekend to consult with Prime Minister Leopoldo Calvo-Sotelo, who was called away from a fashionable Madrid restaurant at midnight Saturday as news of the statement broke. At a press conference Friday, he had asserted there was no risk of another coup.

The document released to the Spanish media said that insults against men with "brilliant and unblemished" military records were considered attacks on the armed forces as a whole and that it was the responsibility of the court-martial alone to hand down judgments.

Informed sources close to the military said that such language reflected widespread feeling in Army circles. Politicians privately view the court-martial, scheduled for spring, with trepidation.

Among the 25 captains who signed were the son of the right-wing extremist Blas Pinar, who heads the neo-fascist New Force Party, and the son of a colonel arrested and indicted after the coup. Twenty-one lieutenants signed the manifesto as well as 54 sergeants and corporals stationed in infantry and artillery barracks here.

Political sources said sponsors of the declaration intentionally limited signatories to the top rank of captain but that it could have been signed by higher-ranking officers from throughout Spain.