Most types of violent crime in Montgomery County fell during the first six months of the year, police announced last week.

But rape and robbery increased by 11 percent and 21 percent, respectively, compared with the same period in 2004, police said.

Montgomery County Police Chief J. Thomas Manger commended his staff in announcing the general drop in violent crime.

"I am encouraged to see an overall decrease in violent crimes," Manger said in a statement. "Much of the credit for these decreases goes to the patrol officers and detectives who have been targeting the locations where these crimes occur, as well as the suspects responsible for these crimes."

Authorities noted one of the steepest rises in commercial robberies, which climbed by 64 percent, with 90 cases reported during the first half of this year. Those include bank robberies.

Police said the Silver Spring and Montgomery Village areas had a high incidence of commercial robbery. Robbers targeted small businesses such as pawn and jewelry shops, dry cleaners and pharmacies. Some of those businesses are vulnerable because they are attended by just one person, police said.

Non-commercial robberies, which include street robberies and residential robberies, increased by 13 percent.

"While we've had an increase of robberies, there has also been an increase in the number of associated arrests," said Skip Baylor, director of crime analysis for Montgomery police. He said police arrested 182 people linked to robberies in 2005 as against 143 during the first half of 2004.

Officers investigated 71 new rape cases during the first half of the year, including a handful reported to have occurred in previous years. Baylor noted that approximately 73 percent of rape cases were reported by people who knew their alleged assailants.

"There's not an overwhelming number of incidents of someone jumping out of the bushes," Baylor said.

Murders decreased by 40 percent, with six murders reported in the county during the first six months of 2005. The second half of the year is off to a bleak start, with detectives working on two deadly-assault cases that occurred after high school football games within a seven-day period.

One of the victims, Kanisha Neal, a 15-year-old Rockville High School student, was stabbed to death in the parking lot of James Hubert Blake High School in Silver Spring last Friday. The other victim, Stephone Wiggins, 23, of Germantown, was beaten with a miniature novelty baseball bat on Sept.16 and died a few days later.

Cases of aggravated assault fell by 14 percent, with 416 cases reported in 2005. Burglary and larceny dropped by roughly 6 percent, with 1,623 burglaries and 7,184 cases of larceny reported this year. Motor vehicle accidents decreased overall, too, although injuries to pedestrians increased slightly.