Michael Vernon Townley, a 35 year old American identified in court as an agent of DINA, the Chilean secret police, was formally charged yesterday with conspiring to murder Chilean diplomat Orlando Letelier.

Investigative sources said Townley is believed to have traveled to the United States from Chile about a month before the murder to contract out the bombing death of Letelier, an outspoken critic of the Chilean military regime. The same sources have said in the past that the actual bombing was carried out by anti-Castro Cuban exiles in the United States who were politically sympathetic to the Chilean government.

Townley, who FBI sources said has been implicated in several other bombings in Latin American, all apparently directed against opponents of the Chilean military government, was ordered held without bond yesterday after prosecutors asked that a $5 million bond be set.

Townley is the first person to be officially charged in connection with the Sept. 21, 1976, murder of Letelier and a colleague, Ronni Moffitt. The two died almost immediately from the Powerful explosive as it ripped up through the floorboard of the car Letelier was driving around Sheridan Circle NW en route to the Institute for Policy Studies, where both worked at the time. The explosion occured within sight of the Chilean Embassy here.

One Justice Department source said that "as many as 10" persons in the United States and abroad could be charged in connection with the murders of Letelier and Moffitt.

The facts upon which the charges against Townley are based were filed secretly yesterday by the federal government, and U.S. Magistrate Henry H.Kennedy Jr.'s decision to hold Townley without bond was make without explanation after a closed session with prosecutors and Townley's attorney, Seymour Glanzer.

Glazer said he was asking for the secret hearing because "I don't feel I'm free to discuss the case" in public.

Glanzer's requesey Eugene M. Propper of the major crimes division asked for the extraordinary high bond of $5 million on Townley because he was an agent of a foreign intelligence service (DINA) that had access to huge sums of money.

"It may be worthwhile for them (DINA) to bail him out," Propper said . He also said the high bond was needed because of the possibility Townley might flee if released, pointing out that in the past Townley has used five different aliases and passports from three different countries to travel into the U.S. on on numerous occasions.

Townley has lived in Chile for most of his life and his wife and two children are Chilean.

Townley has been described in Chile as an electrician who was heavily involved in militant political activities directed against Salvadore Allende, the Marxist Chilean president whom Letelier served as U.S. ambassador. Allende's regime was over - thrown by the military junta in 1973. Townley was indicted for murder in 1973 after an anti - Allende commando raid in which a night was killed, but the military government headed by Gen. Augusto Pinochet that later took over form Allende never sought his arrest.

Townley's name first surfaced in connection with the 19-month-old Letelier murder investigation when he was identified as one of two persons who traveled under false names to the United States on official Chilean passports to meet with persons believed to be involved in the assassination plot.

The other person has been identified as Armando Fernandez Larios, a Chilean army captian attached to DINA. No action has been taken by the U.S. government against Fernandez, who has been identified by some federal sources as a superior of Townley 's whose Chilean nationality keeps him out of U.S. investigator's reach until any formal charges are filed.

The wide ranging FBI and Justice Department investigation into Letelier's murder has been donducted in tight secrecy for the most part but probers decided in February tha public pressure would be helpful in gaining more complete cooperation from the Chilean government.

The U.S. government disclosed at that time that it was asking Chile to produce for questioning the two men who had come into the United States and allegedly met with Letelier bombing suspects.

Agter delicate diplomatic negotiations, Chilean officials produced thef two men for questionning. It then expelled Townley from Chile - April 7, charging that he had violated registration laws by traveling to the country using false documents. FBI agents arrested Townley immediatley on a material witness arrest warrant, and Townley has been held under tight security in the United States since then.

Since Townley's arrest, two anti - Castro Cuban exiles also believed by investigators to be centrally involved in the Letelier murder conspiracy have been arrested in Miami on charges unrelated to the Letelier case.

One of the two, Guillermo Novo, had been a fugitive for about a year after FBI agents investigating Letelier's death asked that his probation be revoked because he had traveled to Chile and Venezuela without informing his probation officer. Novo is on probation for his conviction on conspiring to bomb Cuban facilities in Canada.

The other, Alvin Ross, was subpoenaed last spring to appear before the grand jury here investigating Letelier's death. He was offered immunity from prosecution in exchange for his cooperation with law enforcement authorities but refused to talk and was never presented to the panel as a witness.

Novo was arrested on a figitive warrant, and Ross was arrested by New Jersey authorites on charges in connection with the alleged manufacture and storage of illegal explosives. Federal agents said guns and drugs also were found on the two men at the time of their separate arrests on April 14.

Townley is charged in a complaint, signed by FBI agent L. Carter Cornick, with conspiring" with other persons to murder a former ambassador to the United States from Chile" under a federal law designed to protect current and former foreign officials here. Conviction on the charge carries a maximum possible penalty of life imprisonmemt.

The government must indict Townley within 45 days, unless he waives that time period, or the charges will be dropped. CAPTION: Picture, MICHAEL VERNON TOWNLEY . . . $5 million bond is asked