D.C. police arrested more than 100 people Saturday for alleged narcotics offenses, serious traffic violations or fugitive charges in a one-day sweep aimed at drug trafficking in Southeast Washington, officials said yesterday.

Police said they established inconspicuous observation posts to watch alleged drug trafficking activity near the Condon Terrace and Barry Farms public housing developments and then arrested 57 people on charges of buying drugs and five on charges of selling drugs.

About half the people charged with buying drugs Saturday were from Maryland and several others were Virginia residents. The five suspected drug dealers were identified as teen-agers from Southeast Washington.

Police said they made about 40 other arrests after establishing three roadblocks near the two housing project. Most of those arrests were for charges of driving without a license or driving with a revoked or suspended permit. Seven people were arrested for failure to appear in court for felony or misdemeanor charges.

"I've been wanting to do this for a long time," said Captain Philip O'Donnell, who supervised the operation. "By running several operations at the same time, the people involved with drugs have nowhere to run and nowhere to hide . . . . We will be doing this again in the near future."

O'Donnell said about 70 officers were involved in the operation.

He said that most of the drug arrests were made after police observed cars stopping at curbsides and drivers or passengers making what appeared to be drug purchases. Officers seized marijuana, phencyclidine and heroin valued at a total of $300.

Most of those arrested were freed on personal recognizance or after posting bond.