MEXICO CITY, FEB. 25 -- A series of raids in recent weeks by Mexican police and Army units has broken a major arms and drug-trafficking organization and highlighted the activities here of the notorious Colombian narcotics ring known as the Medellin Cartel.

Using information supplied in part by the U.S. Drug Enforcement Administration, Mexican authorities so far this month have captured more than 360 Soviet-designed AK47 assault rifles of Chinese and East European manufacture, more than 145,000 rounds of ammunition, an assortment of other weapons and drugs, seven light airplanes and a number of vehicles, including a motor home. More than two dozen suspected drug traffickers, including six Colombians, reportedly have been arrested so far in connection with the raids.

According to U.S. and Mexican officials, many of the weapons had been smuggled into Mexico from the United States and were about to be shipped to Colombia for use by the Medellin Cartel in its "war" against the Colombian government. Mexican police said some of the suspects captured so far have confessed that the deal was part of a two-way operation -- using Mexico as a staging area -- to smuggle Colombian cocaine into the United States and send arms to Colombia in return.

"The big payoff was going to be a ton of cocaine," said one U.S. official. Authorities hoped to capture it when it arrived as part of the arrangement. "But we had to take action before the guns got further south."

Federal Judicial Police Commander Guillermo Gonzalez Calderoni said some of those arrested identified the Colombian boss of the operation as Gonzalo Rodriguez Gacha, a flamboyant leader of the cartel who is known as El Mexicano. Gonzalez said the Colombian detainees belonged to the same group that assassinated Colombian Attorney General Carlos Mauro Hoyos last month.

The two-way trafficking arrangement illustrates the range of activity of the Medellin Cartel, which U.S. narcotics officials say accounts for 80 percent of the estimated 220,000 to 265,000 pounds of cocaine smuggled into the United States annually from South America.

It also has raised concerns here about increased violence associated with the drug trade. While drug trafficking groups in Mexico show no sign yet of becoming the antigovernment force that the Medellin Cartel represents in Colombia, Mexican officials lately have expressed growing alarm about their destabilizing potential.

In a report to President Miguel de la Madrid in December, the president of the Mexican Supreme Court warned that drug trafficking "threatens the very roots of the republic." He called on authorities to solve the murder of a federal judge who was killed last September by suspected drug traffickers.

In the latest violence attributed to the drug trade, three masked gunmen assassinated a journalist Monday in the Pacific resort city of Mazatlan, the site of a meeting between Presidents Reagan and de la Madrid Feb. 13. Colleagues said Manuel Burgueno Orduno, 42, who was shot in his home, had been investigating the growing involvement of drug traffickers in Mazatlan's tourism industry.

The unraveling of the arms and drug-trafficking scheme began when Mexican federal police and Army units raided a secret warehouse disguised as a brick factory near the Mexican border with Arizona on Jan. 31. In addition to 11 tons of marijuana and about 4,400 pounds of cocaine, the warehouse outside the town of Agua Prieta in Sonora State contained 100 AK47 assault rifles, six U.S.-made military rifles, more than 65,000 rounds of ammunition, 92 bayonets, six metal detectors and three infrared rifle scopes, police reported.

Three days later, police in Hermosillo, the capital of Sonora, found 83 more AK47s in a motel outside the city. Six Colombians and 16 Mexicans were rounded up in connection with the raids, and arrest orders were issued for 15 accomplices.

Jose Ortega Padilla, the chief antinarcotics official in the attorney general's office here, disclosed in a news conference today that two of the Mexicans arrested were members of the Federal Judicial Police.

Another series of raids in the state of Durango this month resulted in the capture of at least three other suspected drug dealers and the seizure of 180 more AK47s, Ortega said. He said investigations were still under way to determine whether this ring was connected to the Colombian operation.

The raids came after federal indictments in San Diego last month charged 12 Mexicans, including eight members of the Federal Judicial Police, three state policemen and a Mexican customs officer, with smuggling semiautomatic assault rifles and pistols to Mexico from a San Ysidro, Calif., gun shop called Interpol Products. The gun shop owner and two employees were also indicted.

So far, according to the U.S. attorney's office in San Diego, one Mexican identified as a Federal Judicial Police agent, Eduardo Jimenez, is in custody there. The weapons involved in the case match the description of those seized in the Sonora raids.

Mexican officials have complained about the arms smuggling and sent the serial numbers of the captured weapons to U.S. authorities for tracing. But officials here said they have no knowledge of the U.S. charges against the 12 Mexicans, and there has been no word of any action against the policemen named in the indictments.

While Colombian gangs are heavily engaged in drug-trafficking through Mexico and Central America, U.S. officials said, they show no signs of displacing Mexicans as the drug kingpins in their own country. In Mexico, the officials said, the Colombian drug dealers must cooperate, rather than compete, with members of the 28 major Mexican organizations identified by the U.S. DEA as trafficking in cocaine, heroin and marijuana.

In his press conference today, Ortega warned that Mexico "will not permit any foreign clandestine organization to use our territory as a platform" for drug and arms trafficking. He vowed that drug traffickers would never be allowed to gain enough power to threaten the government and "interfere in the political affairs of the country."

According to U.S. officials, Mexican drug traffickers share the authorities' determination not to allow the Colombians to grow too powerful here -- for their own reasons.

In fact, U.S. officials said, a separate indictment in San Diego last month, accusing six Mexicans and six Bolivians of involvement in a massive cocaine smuggling conspiracy, suggests that some Mexican traffickers are seeking to circumvent the Colombian groups that dominate the cocaine trade.

According to U.S. figures, Peru and Bolivia account for more than 90 percent of the estimated 335 million to 414 million pounds of coca leaf grown annually in South America, but most of that production is refined into cocaine in Colombia under the direction of the Medellin Cartel and other gangs.

Among the Mexicans named in the indictment were an Army general, Juan Poblano Silva, who commands the military district in the state of Puebla, and a member of his staff, Lt. Col. Salvador de la Vega.