You are the lucky recipient of two free tickets to the Washington Redskins-Cincinnati Bengals game, the letters read, and to collect your prize all you have to do is attend a pregame brunch at the Washington Convention Center.

About 100 gleeful persons responded yesterday. Garbed in scarves, gloves, overcoats and caps that read "Riggo's Rangers," most had visions of lounging in the windy stands, socking down a few beers and hotdogs and cheering on the home team to victory.

It turns out they had overdressed for the occasion. While they waited for their tickets in a small room at the Convention Center, eating pastries and drinking coffee next to posters that urged "Let's party!", an emcee in white tails and top hat announced that he had a "surprise": They were under arrest.

The ticket winners stopped singing "Hail to the Redskins" as 28 deputy U.S. marshals and D.C. police officers, dressed in flak jackets and carrying shotguns, marched in, handcuffed them, and put them on a bus that went to D.C. Superior Court instead of to RFK Stadium.

It was an elaborate sting called Operation Flagship, and law enforcement officials said it netted 101 fugitives wanted in connection with more than 170 outstanding criminal arrest warrants in the Washington area.

"They went for it hook, line and sinker," said an exuberant Herbert M. Rutherford III, U.S. marshal for the District. "There was everything from laughs to tears. They were totally caught off guard" by the scam, which officials said was perhaps the largest and most successful of its kind ever staged.

D.C. police Chief Maurice T. Turner Jr. said the suspects are "responsible for a large percentage of the criminal offenses in our communities" and that their arrests "will no doubt have an impact on our daily crime rate."

The sting idea was conceived about three months ago, Rutherford said, and letters from a fictitious company called Flagship International Sports Television Inc. were sent about seven weeks ago to more than 3,000 persons with outstanding warrants.

The name of the company stands for FIST, the acronym for the Marshal Service's Fugitive Investigative Strike Team.

The correspondence that lured the unsuspecting targets to the Convention Center announced the birth of "Washington, D.C.'s all-sports television channel" and informed the recipients that their names had been selected from a "computer clearinghouse list" of area residents.

The letters promised that a drawing would be held at the Convention Center "for 10 lucky winners to receive 1986 Washington Redskins Season tickets! In addition, a Grand Prize Drawing for a one-week, all-expenses-paid trip to Super Bowl XX in New Orleans, Louisiana, will be given to a lucky person and three of their guests!"

"I'm going to sue for false advertising!" one person yelled from inside a bus parked near the old D.C. Superior Court building, where the targets of the sting were taken for processing.

Others from the bus joined in a chorus of screams, some venting their frustration, many proclaiming their innocence and a few finding humor in their plight:

"Are we going to the game after we get out?"

"Tell them we appreciate the invitation!"

"I thought I was going to the Super Bowl!"

"I'll tell you what kind of a party it was," said one suspect, still sporting a blue and white patch announcing: Hello, My Name Is . . . .

"As soon as they invited me in there they put a 12-gauge shotgun in my face and said, 'Freeze.' "

Officials said the roundup nabbed people wanted in connection with 15 warrants for assault, five for robbery, six for burglary, four for escape, 19 for bond default or bail violation, 18 for narcotics violations, 59 for probation or parole violation, two for fraud or embezzlement, one for a weapons violation and 41 for a variety of charges from rape to arson to forgery. Officials said the arrests were made without incident and that no one was injured in the operation, which started at 9 a.m. and ended about two hours later. They said two handguns were confiscated along with an undetermined amount of narcotics.

Police arrested five persons who were later released when it was discovered that they were not wanted on a warrant, according to D.C. police spokesman Lt. William White III.

He said the persons, including the son of a man wanted in the District for murder, had gone to the Convention Center with a letter sent to someone else and were released after their true identities were confirmed.

More than 160 police and deputy marshals took part in the operation, many posing as ushers, caterers, cleaning personnel and Flagship officials. When the suspects entered the Convention Center, they registered at a booth, then were led in groups ranging from 12 to 18 persons to a small party room on the second floor.

The emcee, a deputy marshal in a chicken costume, and another dressed as an Indian made a promotional pitch for the fake company and kept the suspects entertained until the emcee said the code word -- "surprise" -- at which point marshals and police hiding nearby jumped out and made the arrests.

Stanley E. Morris, director of the U.S. Marshals Service, said there are "more than a quarter of a million fugitives from justice at large on any given day" in the United States, and that "stings are a safe, clean, creative way to inexpensively get these people off the streets." He said the D.C. operation cost about $22,100.

Officials said that in many cases a suspect has moved and marshals are unable to locate him or her. However, the officials said, mail frequently will be forwarded to the suspect's new home.

In addition, according to one deputy, it is much safer to arrest a suspect away from home when he or she does not expect it.

"These people weren't going to the Convention Center to do business," the deputy said. "They were going to a party to have a good time."