At least seven patrons of the Washington Hilton Hotel were victimized Monday night by a burglar or burglars who obtained about $4,050 in jewelry and $560 in cash and travelers checks, D.C. police reported.

Police said the burglaries all took place between 6 p.m. and midnight, when none of the victims were in their rooms. In each case, the thief either used a duplicate key or used a smooth, flat object such as a playing card to "slip" the lock open. Police said none of the doors had been forced.

A similar burglary was reported at nearby Madison Hotel, where Omar and Hiba Fathaly of Libya had $5,800 in jewelry stolen from a jewel case in the bathroom.

The burglaries at the Hilton occurred on the fourth, fifth, sixth and eight floors. One victim was Harry M. Osah, the managing director of the Nigerian Industrial Development Bank, who lost 28 pieces of jewelry valued at $2,900.

Police said Osah told them he purchased $1,360 worth of the jewelry at a downtown store Monday afternoon. A thief also obtained a $650 diamond pendant from an Oklahoma City man, $500 in jewelry from a Long Island, N.Y., man, and $450 in travelers checks from a Paris man.

A traveler from the Netherlands also reported 200 guilders stolen, worth about $82.

In most of the Hilton burglaries, police said the thief went through the victims' luggage. One person reported no theft, but said $75 in damage was done to a suitcase by a would-be burglar.

Police said a similar group of burglaries took place in the spring at the Hilton, and travelers checks taken from hotel patrons later were recovered in Atlanta, Miami, Chicago and New York.

There have been no arrests and investigators said they have no suspects.