Concern rose today over the condition of France's 62-year-old ambassador here, who has been held hostage by militants of the Popular Revolutionary Bloc in the French Embassy for three weeks.

Meanwhile, at least four persons were reported killed last night in continuing violence.

French envoys negotiating for the release of Ambassador Michel Dondenne and five others have not seen the ambassador, who previously came to the embassy's second floor window daily, since early in the week. Sources close to the negotiations said that Bloc leaders cited "security reasons" for his failure to appear.

The French Embassy was occupied by the Bloc, a peasant-student coalition the government charges with ties to leftist guerrillas, on May 4.

Other Bloc militants occupied the Venezuelan Embassy on May 11. They have been left alone inside since their eight hostages escaped Sunday, although the government has cut off food and water supplies in an attempt to force them out. Last Tuesday, 14 youths were shot by security forces when they tried to carry food to those inside.

That incident, sources said, has "spooked" negotiations over the fate of the French Embassy hostages. At the time, the sources said, negotiations are stalled over Bloc Refusal of offers of asylum in another country for the occupiers. The El Salvador government has repeatedly refused to agree to the amnesty from prosecution that the militants have demanded.

Militants inside the Venezuelan Embassy today told reporters, who are allowed to speak to them through a window, that they have nearly run out of packages of crackers, which have been their only food since Sunday.

The militants said they have rationed themselves to four crackers each per day, but would run out by Saturday morning. The group said they collected water on an open patio during a heavy rain last night.

The militants said their resolve to stay inside the embassy - which is considered unapproachable foreign territory by police - had been strengthened by those shot on the street outside Tuesday.

"What fortifies us," one reportedly said, "is the knowledge that we are political prisoners, undergoing a form of torture."

Education Minister Carlos Antonio Herrera Rebollo was killed Wednesday morning by members of the guerrilla Popular Liberation Front in retaliation for the embassy shootings.

The militants at the Venezuelan Embassy pleaded with reporters, who they said were their "only hope and contact with the rest of the world" to describe their struggle for the "freedom from exploitation and oppression of the Salvadoran people."

They charged the government of Venezuela with abandoning them to starve and having more interest in "world image and presitge" than in human rights. Although Venezuela continues to guarantee their physical security inside the embassy, its government stopped negotiating with the militants when the hostages escaped.

Bloc leaders said yesterday that they has asked the United Nations and the government of Panama to intervene to supply the militants with food and medicine, but had received no reply.

Both the El Salvador government and the Bloc have refused to deal directly with each other. The government did not invite representatives of the Bloc, which claims 30,000 members to a "national forum" of talks with political and social groups here. The government has declared the Bloc an illegal organization.

The talks, called by President Carlos Romero in an effort to discuss the current situation and solutions, got off to an inauspicious start Thursday when the country's main unions and opposition political parties refused to attend.

The opposition cited a state of siege, declared Wednesday, and what it said are repressive conditions "incompatible with democracy" as reasons for its refusal to attend.