An assorted group of civilians was brought to trial yesterday before a military tribunal on charges of subversion.

In the steamy atmosphere of a squash court on a military camp, newspaper executive Eduardo Olaguer was accused of being the brains behind an urban guerrilla group called "Light-a-Fire Movement." This group, allegedly committed to the overthrow of President Ferdinand Marcos' martial law government, is believed to have been responsible for several cases of arson at Manila hotels last year. The government is alleging that the organization is funded by United States-based Filipino exiles.

The military is accusing Olaguer, 44, whose detention since December was investigated by Amnesty International, and 19 others of sending bombs to two Cabinet ministers and setting fires to three properties owned by friends of Marcos.

A floating casino in Manila Bay and one hotel were completely destroyed last year; two other hotels and a shopping arcade were damaged in fires attributed to the group.

Only 10 of the accused appeared in court yesterday, many of whom were working for Alaguer at Business Day, a newspaper he managed. Explosives and weapons were allegedly found in some of their homes.

Originally two Americans were also charged. One, Steve Psinakis, brother-in-law of newspaper publisher Eugenio Lopez Jr., a foe of Marcos, is in the United States. The other was Ben Lim, an American of Filipino descent.

Lim, 62, of Seattle, died last month of a heart attack a few days before he was to be released. Highly placed sources said Lim's release was arranged after he agreed to confess and to implicate other people in alleged plot.

What surprised observers about the group was that most of them are highly successful middle-class executives. They include Gaston Ortigas, former dean of the prestigious Asian Institute of Management, patterned after the Harvard Business School.

The U.S. Embassy today rejected the Philippine government's request to extradite Ortigas, Psinakis and a fourth missing suspect on grounds that there is no extradition tready between the two governments.

The oldest person put on trial is a sprightly 64-year-old grandmother of 20.

Esther Jimenz is jointly accused with her husband Othoniel, a vice president of an insurance company.

At yesterday's hearing, before Olaguer and the rest could make their plea of innocence, the military prosecutors and the battery of defense lawyers became locked in a near shouting match over the tribunal's legality.

The defense lawyers were led by veteran opposition politician Lorenzo Tanada, 81, and human rights lawyer Jose Diokno Tanada asked that the charges be dropped on the ground the military tribunal had no legitimacy since the martial law government of Marcos was illegitimate. He received a round of applause.

The defense also maintained that military tribunals were no longer allowed to try cases involving possession of firearms. But they were surprised when the prosecutors produced a copy of a letter from Marcos dated in April allowing the tribunal to hear the Olaguer case. Under the martial law system Marcos can change laws by issuing so-called letters of instruction.

Diokno insisted that the letter was not law since it was not published. The hearing was adjourned until next week for the prosecutors to answer defense motions.