Six would-be hijackers were arrested in two incidents in Florida over the weekend as authorities sought to stem an unprecedented rash of sky piracies to Cuba.

The arrests came as armed, federal marshals were assigned to the air on selected commerical flights and security officers tightened procedures on the ground in an effort to thwart further hijackings.

Two of the weekend arrests were made yesterday morning in Miami and four Saturday evening in Tampa. The six suspects were disgruntled Cubans refugees who came to the United States in last spring's "Freedom Flotilla," spokesmen for the FBI and the Federal Aviation Administration said.

The arrests capped a week in which six U.S. jetliners were hijacked to Cuba, including three piracies on Saturday alone. The hijackers were all recently arrived Cuban refugees, federal law enforcement officials said.

"Six hijackings in one week! We have to stop that. I hope these apprehensions would deter any future attempts," said Tampa FBI agent Dick Ross.

Ross and others credited the arrests to the beefed-up security procedures at Florida airports and the restoration of a once-discarded, anti-air-piracy weapon, the "behaviorial profile" scan.

The profile, abandoned in 1973 when metal detectors were brought into airports, consists of a visual check of boarding passengers by airline employes trained to look for certain characteristics.

FAA spokesman Fred Farrar said the profile was instrumental in the arrests yesterday of Jose Antonio Pablo-Lugones, 37, and Hector Pinero, 41, who were attempting to board Air Florida Flight 41 en route from Miami to Key West.

According to Farrar and Miami FBI officials, Lugones and Pinero were spotted by Dade County Public Safety Department officers on duty in the boarding gate area.

"The officers noticed that the individuals had protrusions in their clothing," a Miami FBI official said. "They questioned the two men and subjected them to a more intensive search," he said.

The "more intensive search" showed that one suspect had a string around his waist that was attached to a beer bottle of gasoline hidden in his trousers, said the Miami FBI spokesman. The second suspect had a "pintsized whiskey bottle in his jacket" that also contained gasoline.

The spokesman conceded, however, that the profile check also has its drawbacks:

"Three people were actually arrested in Miami. But it was later determined that one of them wasn't involved. He was only talking to them."

Lugones and Pinero had entered the United States in May as part of the Cuba-to-Key West boatlift, according to the FBI. Both had been living in Union City, N.J., and had traveled to Miami last Tuesday.

"One of them said he wanted to go home because he left his immediate family in Cuba. The other said he wanted to return because he couldn't find a job here," the FBI spokesman said.

The Saturday arrests in Tampa occurred after an X-ray screening device detected "a heavy mass" in a small travel bag being brought aboard Eastern Airlines Flight 115 -- Tampa to Miami -- by one of four Cuban men, the FBI said.

The "heavy mass" turned out to be four, small plastic "bleach-type" bottles containing a flammable liquid, according to Tampa FBI spokesman Ross.

He said Tampa airport officials have begun detailed checks of carry on baggage. That, plus the use of the profile procedure, resulted in the arrests Saturday night of Antolin Acevedo, 35, Aurelio Acevedo, 38, Eugenio Areu-Del Campo, 29, and Alvarino Nelson-Gonzalez, 30, Ross said.

Two of the tampa suspects had been living in Tampa and two in Miami.

The Miami suspects each were charged with attempted destruction of a commercial aircraft, attempted sky piracy, conspiracy to commit sky piracy and attempting to bring an incendiary device aboard commercial aircraft. Each count carries a maximum 20-year sentence.

The four men arrested in Tampa were each charged with attempting to bring incendiary devices aboard a passenger plane, and officials said more charges may be forthcoming.

"They all said they were homesick and wanted to go back to Cuba . . . They had been cutting sugar cane in south Florida," Ross said.

Last night, the State Department said it has "repeatedly approached the Cubans . . . to urge that they permit Cuban citizens who have come to the United States by boat to return to Cuba in an orderly and safe way.

"Thus far, we've had nothing from the Cubans but rebuffs on this issue," the department said.

A spokesman said the department's requests for the names of the people who hijacked the airliners also has been ignored.

The flying law officers assigned yesterday to commercial flights are FAA employes who have received special training and who have been deputized as U.S. marshals, Farrar said.

He said he could not say how many marshals are being placed aboard the commercial flights. Nor could he, "for security reasons," say exactly what airlines are affected.

Some of the marshals will be uniformed. Others will be in plainclothes.

The sky marshal program also was used in the early 1970s to foil hijackers, and, like the profile scan, had been abandoned.

In all, 22 Cuban refugess made it back to their homeland in the six successful hijackings, FBI officials said yesterday. Eleven of the sky pirates returned to Cuba in the three separate hijackings Saturday -- a record for one day.

Six refugees commandeered an Eastern flight from Miami, four took over a Republic flight from Miami, and one diverted a Delta flight from San Juan, Puerto Rico, in the Saturday incidents.

All of the hijackers are in the custody of Cuban authorities, according to the FBI, which based its report on "Spanish-speaking sources."

The aircraft and their passengers were returned safely, the FBI officials said.