CARACAS,VENEZUELA, JUNE 16 -- Colombian guerrillas attacking across Venezuela's mountainous northwestern frontier killed 15 members of a National Guard antidrug unit today, military authorities announced.

Defense Minister Jose Rafael Cardozo Grimaldi tonight issued the report after inspecting the battle zone. He said the Venezuelan troops fought back and killed 33 suspected drug traffickers. Ten guardsmen were wounded. Two earlier Defense Ministry communiques had put the death toll among troops at 10 and 18.

The rugged Sierra de Perija region where the attack took place borders on Colombia's most fertile marijuana-growing area. It has been the scene of several recent confrontations between the Venezuelan armed forces and drug traffickers, but today's shoot-out was the first battle with so many casualties.

The attack is the latest in a number of drug-related incidents underscoring what observers have been suggesting for months -- that Venezuela is now being pulled into South America's drug empire.

Authorities said today that about 85 "narco-guerrillas" opened fire on guardsmen searching out and destroying marijuana and coca plantations concealed along the steep slopes of the 75-mile-long Sierra de Perija range in the Venezuelan state of Zulia.

Claims by military sources that the attackers were members of the M19 and other left-wing antigovernment guerrilla groups in Colombia could not be confirmed. Nor were there any firm figures on guerrilla casualties. There have been allegations in Colombia for some time that the M19 guerrillas can be hired for protection services for drug traffickers.

Three weeks ago, the same guard unit that came under fire today discovered a 320-acre plantation of marijuana and coca near the town of Machiques, about six miles from the Colombian border.

Last November, troops patrolling the region discovered 26 tons of marijuana neatly pressed, packaged in aluminum foil and stacked for shipment. That followed an earlier find in the same area of a 250-acre marijuana farm and some test plantings of coca bushes.

Colombia's aggressive defoliation campaign against marijuana plantations apparently has pushed growers over the border. Authorities said marijuana grown in Venezuela is carried by donkeys back into Colombia and then exported through the port of Santa Marta.

Venezuela's failure to keep the traffickers out of the Sierra de Perija pointed up the country's weakness before the onslaught of hugely rich, tightly organized drug dealers.

During the oil boom years this OPEC nation's high standard of living made it less likely that criminals and corrupt officials would turn to drug trafficking. But as oil prices remain low and unemployment rises, the lure of cocaine's easy cash has taken on a new luster.

In February, detectives arrested Congressman Hermocrates Castillo after they discovered 11 pounds of cocaine in the trunk of his official car. Venezuelan President Jaime Lusinchi said the case left him "profoundly worried."

Lusinchi has cause for concern. In October, U.S. Drug Enforcement Administration officials in Florida found 6,800 pounds of high-quality cocaine welded into two shipping containers transported from the Caracas port of La Guaira on the Venezuelan freighter Marlago I. It was the largest cocaine seizure in U.S. history.

And even as antidrug officers from Venezuela and Colombia were winding up a November strategy session on border drug traffic, Venezuelan National Guard troops were discovering major cocaine operations in nearby Tachira state, just south of the Sierra de Perija and fronting on Colombia. In one week the guardsmen collected 162 pounds of cocaine in three separate incidents.

Now hardly a day passes without new drug discoveries. Venezuela serves the drug traffickers as a bridge between coca plantations in Bolivia and Peru, cocaine refineries in Colombia and consumers in Europe and the United States. With its excellent highways, many small airstrips and half-dozen Caribbean ports, Venezuela is a natural conduit for narcotics.

Traffickers have been slow to make the Venezuelan connection. Until recently, cocaine traders preferred to ship directly from the countries where their reign over local officials greatly reduced the chances of prosecution.

But mounting pressure in Boliva, Peru and Colombia has pushed the traffickers to seek new trade routes in Venezuela.

The main port of entry is the dusty Colombian border town of Cucuta, in Tachira. The Venezuelan National Guard maintains a roadblock on the other side, but one antinarcotics officer who asked not to be identified called the roadblock "a swinging door." He said, "People come over with sacks on their backs. There's no control at all."

The trip can be highly profitable. A kilogram (2.2 pounds) of cocaine costs $4,000 in Cucuta, according to police sources. Smuggled to the Venezuelan side, the price jumps to $6,500. The street value in Miami reportedly is four times that amount.

Although Venezuela arrived late on the drug-smuggling scene, the nation is now playing a major role. A well-placed Venezuelan policeman who asked not to be identified said that every month a ton of cocaine moves through Venezuela.

Lusinchi has taken a strong stand against drugs, using an appearance before the United Nations in 1985 to declare war on trafficking. Lusinchi's government passed a major criminal law reform in 1984 that lengthened prison terms for traffickers while establishing a presidential commission to coordinate the antidrug battle.

The government's nagging nightmare is that more and more of the cocaine and marijuana entering the country will be consumed here. Many youths in the cocaine-exporting nations of Bolivia, Peru and Colombia now use bazuco, the cheap coca paste smoked in cigarettes.

A presidential commission is now launching a campaign aimed at rallying patriotic sentiment against drug dealers. Commission President Bayardo Ramirez said drug traffickers are a modern version of the Spanish conquistadors who ravaged the continent centuries ago.