alvadoran military spokesmen said today that the embattled town of Perquin and its small government garrison in the guerrilla-dominated northeast corner of El Salvador have fallen to rebels as the war here continues slowly, but is steadily escalating after the brief respite of April and early May.

The rebels took the town Saturday and have successfully held it since, according to Col. Marco Aurelio Gonzalez of the armed forces press office. Earlier guerrilla claims to that effect were denied.

The village and surrounding settlements, which were captured and successfully held for 10 days last August, contain about 3,000 people. The garrison of soldiers and National Guardsmen was "not smaller than 20," in addition to paramilitary Civil Defense units, Gonzalez said. The guerrillas claimed to have killed five, wounded 12 and taken six prisoners. Gonzalez would not give specific figures.

The move against Perquin is apparently a rebel attempt to offset the impact of a continued, massive government offensive about 60 miles to the west in Chalatenango.

The fighting there, which began on May 29 and is the first combat by a batallion of Salvadoran troops trained at Ft. Bragg, N.C., earlier in the year, remains inaccessible to journalists.

The Chalatenango operation, the biggest military "clean-up" in the two-year history of the war here, has been criticized privately by some Western observers who say it is a waste of resources to attack the guerrillas in the economically insignificant, mountainous border region with Honduras.

But the reports of the guerrillas' clandestine Radio Venceremos suggest, indirectly at least, that the operation is hurting them.

Almost from the beginning of the operation guerrilla broadcasts have alleged a major massacre by the government forces, saying as many as 600 civilians were killed around the guerrillas' Las Amates Base.

Some observers here believe this may indicate that rebels of the Popular Liberation Forces who have their strongholds in Chalatenango may have been forced to abandon whatever civilian population they had offered protection from government troops.

The guerrilla radio has also said Honduran troops are involved in this operation and were involved in the alleged massacre, not only by sealing escape routes across the border but actually crossing into El Salvador.