WASHINGTON-The government tightened security at federal buildings and offices throughout the nation yesterday after a series of terrorist bombings.

A spokesman for the General Services Administration, manager of federal civilian installations, said he did not know whether the alert was prompted by any secret information that might warn of further attacks; nor did he know how long the alert might last.

The GSA placed guards on patrol outside federal buildings and in parking areas; locked all but the main entrances; and began denying entrance to persons carrying "suspicious packages" unless they permitted inspection of the parcels.

A spokesman said General Services Administrator Robert L. Kunzig ordered the security alert late Monday night and it was placed in effect Tuesday.

He said the GSA had been studying security problems "for some time" because of bombings against both government and non-government buildings. A federal office building in Rochester, N. Y., was hit Monday.