Four activists subpoenaed to testify about bombings at the U.S. Capitol and other federal buildings here said yesterday that they will refuse to answer questions from a federal grand jury investigating the attacks.

The four, who identified themselves as current or former members of the John Brown Anti-Klan Committee, said they had no knowledge of the bombings but sympathized with groups that have claimed responsibility.

"We recognize these bombings as a legitimate form of resistance to U.S. militarism. We have and will continue to publicly state our support for them, together with other militant actions -- demonstrations, civil disobedience, draft resistance . . . . ," the group said in a written statement.

The four activists are Steven Burke, 25, of Washington, and Julie Nalibov, 24, Christine Rico, 24, and Sandra Gayle Roland, 25, all of New York.

All four appeared before Chief U.S. District Judge Aubrey E. Robinson Jr. in a closed session, during which their lawyer asked that the subpoenas be quashed, according to sources.

The group also asked that federal law enforcement officials be forced to disclose wiretapping or other electronic surveillance, if any, of the group. Robinson made no immediate decision on the motions.

The activists said an organization called the Armed Resistance Unit has acknowledged responsibility for three of four such bombings in the last two years.

The blasts occurred in April 1983 at the War College at Fort McNair, in August 1983 at a computer complex at the Washington Navy Yard and in November of the same year at the Capitol. The Capitol bombing was to protest the U.S. invasion of Grenada, the activists said yesterday.

In a fourth explosion last April, the four said an organization called the Red Guerrilla Resistance bombed the Navy Yard officers' club to protest Operation Ocean Venture 84, which they described as a practice invasion of Central America and the Caribbean.

There were no injuries in the bombings.

The four could face civil or criminal contempt charges and jail terms if Robinson orders them to cooperate in the grand jury's investigation and they refuse.