The Immigration and Naturalization Service has started legal action aimed at the deportation of four alleged war criminals living in the United States.

The proceedings - three deportation hearings and one denaturalization hearing - are the first of several cases under investigation by the INS to be brought to trial.

The defendants are Karlis Detlavs a Latvian who lives in Baltimore; Boleslavs Maikovskis, also Latvian and a resident of Mineola, N.Y.; Villis Hazners, another Latvian living in Newark, N.J., and Frank Walus (also known as Wallace), a German-born Chicago resident.

The four, all elderly men who have been in the United States since the late 1940s or early 1950s, have been accused of complicity in murder and other crimess against Jews during Nazi Germany's World War II occupation of Eastern Europe.

To move against the seven successfully, the INS must prove that they were involved in war crimes and that they concealed this information through fraud or misrepresentation when they entered the country or were naturalized.

The three Latvians have been living in the United States as resident aliens and theoretically could be ordered deported following a decision against them in an Immigration Service hearing.

Walus, who holds U.S. citizenship, would have to be stripped of his citizenship before he could be subjected to a similar deportation hearing. Revoking the citizenship of someone who became naturalized requires a trial in a U.S. District Court.

Each of the proceedings is expected to include testimony from eyewitness survivors of Nazi war crimes. Manyof the witnesses have been brought to the United States from Israel specifically to testify.