Death squad activity in El Salvador, which sharply declined during December and January, is increasing again, says the Human Rights Office of the Roman Catholic Archbishop's Office here.
The Human Rights Office, whose statistics are widely regarded as reputable, contends that death squad activity fell after United States Vice-President George Bush visited El Salvador last Dec. 11, but that it increased toward the typical level in February.
Fifty-eight murders by death squads were recorded in February - higher than the average 30 to 40 victims per month, the archbishop's office says.
Vice-President Bush reportedly demanded during his December visit that Salvadorean officials take action against the death squads. He reportedly promised the Salvadorean government that if his demands were met, the Reagan administation would substantially increase military aid to this country.
''In December there were only 26 recorded death squad victims and in January we recorded 22 victims,'' says Maria Julia Hernandez, director of the Human Rights Office. ''We attributed this drop, the lowest monthly totals we have recorded in many years, to the pressure exerted by Vice-President Bush.''
Bush also reportedly asked that action be taken against several specific Salvadoreans. One of those he named, according to reports, was Capt. Eduardo Alfonso Avila, who was implicated in the murder of two US labor advisers in January 1981. Captain Avila was arrested in January but was released last week and cleared of all charges.
More than 38,000 civilians have died at the hands of government forces since 1979, according to the Archbishop's office. The office recorded 58 killings in February and 34 in March.
A decline in death squad activity was noted in January by United States Ambassador to El Salvador Thomas Pickering in an internal cable to the State Department. The ambassador cited the drop as an improvement in the human rights situation in El Salvador.
But while killings by death squads decreased, at least briefly, the numbers of killings of civilians by Salvadorean Army troops increased, according to the archbishop's office. Also there have been numerous killings of rightist political and civilian figures, apparently by leftist rebels.
(The Salvadorean Army contends that so-called civilians killed by its forces are massas - groups of unarmed civilians who provide logistical support for guerrilla fighters and who often live in close proximity to rebel camps.)
Although the Archbishop's Human Rights Office cites an increase in death squad activity, a spokesman for the US Embassy does not note any change.
''I am not aware of an increase in death squad activity,'' embassy spokesman Greg Lagana says, ''but it is our belief that although the numbers may rise and fall, the long-term trend points toward a general decline.'' Return to normal levels of death squad activity has been attributed by some observers here to increased unrest by the working class. Work stoppages and strikes have been widespread for the past month.
''The mechanism of state terror usually increases to counter any agitation,'' a political analyst says. ''The death squads are one of the best instruments the military and wealthy elite have devised to maintain the climate of terror and repression. Despite all the pleading by George Bush, no one in this government is ready to abolish the death squads.''
Bush reportedly demanded during his visit here that the Salvadorean government exile or expel about 20 civilian and military leaders involved with death squad activity. He held meetings with directors of the Treasury Police and National Police, who are alleged to have close ties to the death squads.
Shortly after his visit, the Salvadorean Army transferred three military officers singled out by Bush to diplomatic posts abroad.
These officers are Maj. Jose Ricardo Tozo, Lt. Col. Aristides Alfonso Marquez , and Lt. Francisco Raul Amaya Rosa. Other death squad leaders named by Bush apparently remain in Salvador without reprimand. The US Embassy has expressed ''disappointment'' over release of Captain Avila.