At dawn recently, a small band of counterrevolutionary guerrillas stormed up a prominent hill near here, overlooking the Honduran border.

A few made it as far as the baked earth of the crest, known locally as "the Hill of Sighs," before the attack was driven back by Nicaraguan sentries firing from a five-foot trench. According to the Nicaraguan troops, one intruder was shot and killed while the others fled back down into the tall grass that had shielded their approach.

The clash involved fewer than a dozen men and arms no larger than assault rifles. But Nicaragua's Sandinista leadership says 50 assaults have been launched since July by commando teams striking from camps just inside Honduras -- or clandestine positions within Nicaragua.

Nicaragua says the raids are part of a destabilization campaign covertly financed by the United States, aided by the Honduran Army and officered by former soldiers from the defeated Nicaraguan national guard. [A State Department spokeswoman refused to comment on the charge of U.S. involvement, saying only that the department does not discuss intelligence matters.]

Attacks have resulted in the deaths of about 45 Nicaraguans, mostly civilians, and the abduction of about 65, according to a government count. Foreign analysts in Managua, the capital, put the toll higher, estimating up to 250 deaths over the past year.

The harassment also seems to have convinced the Sandinista leadership that there is truth in reports that U.S.-backed forces seek to chip away at government authority near the border and perhaps seize a slice of territory to declare it "liberated" from the leftist, 3-year-old Sandinista rule.

This month, the government declared the entire border zone a "military emergency area," restricting travel and imposing a form of martial law.

Locally recruited border guards, posted 24 hours a day in the trench sliced into this mound, peer through binoculars at hills across the little Guasaule River that marks the Honduran border. In San Pedro del Norte, 20 miles north of here, schoolchildren practiced scrambling into underground shelters dug by local militiamen to protect against mortar attacks. An Army spokesman said more than 20 81mm rounds crashed into the village last month.

Reports from frequent travelers to the area say the Army has brought up to the border some tanks or armored personnel carriers to serve as gun positions against any large-scale attacks. But during a recent trip along the border from Somotillo north to San Pedro, only truckloads of youthful soldiers carrying AK47 assault rifles were visible -- driving up and down the twisting gravel road along the frontier hills.

Army spokesmen say attacks and defense measures are of a larger scale farther north, in the Nueva Segovia area, and particularly in the desolate Zelaya region that stretches from Nueva Segovia's sharp mountains down to the steamy Atlantic coast.

The government forcibly transported about 12,000 Miskito Indians from their traditional wandering ground along the Coco River last December, charging they had collaborated with counterrevolutionary guerrillas or, alternatively, were in danger from the attacks.

Most were trucked inland to a government-run settlement. But almost as many fled northward into Honduras, forming a recruitment pool for anti-Sandinista forces at the Mocoron refugee camp near Puerto Lempira in southeastern Honduras, according to reliable reports from foreign sources in the area.

Nicaragua says that to guard against infiltration, its Army has set up several bases along the Coco River in what is now nearly a population-free strip stretching inland from the Atlantic toward the Nueva Segovia mountains.

The operation, commanded from Puerto Cabezas on the coast 70 miles south of the border, underlines the government's concern about the undeveloped Zelaya region with its traditionally independent-minded Miskito population.

Jaime Wheelock, agriculture minister and one of nine officers who run the ruling Sandinista front, said in an interview that in late summer the Army found itself facing three battalions -- totaling 1,500 counterrevolutionaries -- in three areas of Zelaya. Some were as far as 100 miles south of the Coco River border, with camps and plans to set up "liberated territory," Wheelock added.

While the government frequently denounces small-scale incursions, Wheelock's charge of an ensconsed operation of this dimension was unusual if not unprecedented.

The Army dispersed the three units, he said, but still engages in small-scale clashes with remnants of the battalions. He said they are equipped with U.S.-made M79 grenade launchers and AR15 semi-automatic rifles.

As a result of captured plans, Wheelock said, the Sandinista leadership has set up what he called a "bastion" in Nueva Segovia Province in addition to the cleared zone along the Coco River. Ironically, the rugged Nueva Segovia area was the stronghold of Augusto Cesar Sandino, a revolutionary of half a century ago who inspired the country's current rulers.

Sandinista leaders say they expect more fighting along the border despite pledges last week by President Roberto Suazo Cordova of Honduras and his foreign minister, Edgardo Paz Barnica. Both promise that the Tegucigalpa government will toughen control along its borders, implying that the counterrevolutionary commando units will be impeded.

But Nicaraguan officials say the forces could refuse attempts to rein them in and, already equipped and in place, try to strike across the border. "These things have a dynamic of their own," said a high Sandinista official.

"A war could start with a little conflict, a certain situation," Defense Minister Humberto Ortega said in a meeting with reporters. "But one does not know when it would end, or where it would end."

In a formal protest to Honduras last week over the latest commando attack in Nueva Segovia, the Foreign Ministry criticized "what appears to be a negligent way of proceeding, on the part of your government's authority, with respect to the genuine application of its intentions for neutrality and peace."

"The problem is that the border situation is exactly the same," said Nora Astorga, a Foreign Ministry official.[On Thursday, news services reported, Nicaragua again protested to Honduras, charging that insurgents based there killed five soldiers in clashes Monday and Tuesday. In a separate announcement, the Nicaraguan Defense Ministry said Capt. Laureano Mairena Aragon, chief of the border patrol, was killed in another attack Wednesday.]