A group of 30 slogan-chanting demonstrators yesterday marched in front of the First National Bank of Boston on Federal Street charging that the bank's investment policy supports a military dictatorship in Argentina.

Claiming that the bank is the largest United States investor in Argentina, the group chanted "The First National's investments support political murder." Ruth Robinson, a spokeswoman for the group, said over 100 political murders have been covered up by Argentina's military dictatorship in the last three months.

John Holbrook, one of the demonstrators, said that the demonstration's date was chosen to coincide with the visit in Boston of Juan Carlos Corral, leader of the Partido Socialista de los Trabajadotes and a well-known Argentinian left-wing politician who has been placed on the published death-list of the rightist Anti-Communist Alliance.

"There is evidence to show that the Alliance is just a group of policeman without their uniforms. Holbrook said, He said Corral was asked to speak at the demonstration, but declined the invitation.

Ernest D. Wamba, lecturer on Afro-American Studies, was listed by the group as a sponsor of the demonstration, but he said yesterday that he had not agreed to be a sponsor, although he said that he is concerned about political repression in Argentina.

Bank officials declined to comment on the demonstration.