SPRINGFIELD, Ill. – Serious crime in Illinois fell again last year, but murders rose unexpectedly and violent crime was more of a problem in rural parts of the state, new state data shows.

Police throughout Illinois reported 467,372 violent and property crimes in 2006, a 1.7 percent drop from the year before and part of a multiyear trend of declining offenses.

But murders were up for the first time in five years, thanks to a doubling in rural counties and an increase in the Chicago area. Robberies increased more than 2 percent and violent crime in rural areas went up for the fourth time in five years.

Meanwhile, arrests dropped significantly statewide, with murder arrests down 16 percent and drug arrests dipping slightly.

State officials say they’re pleased that overall crime numbers continued to improve but other trends are a reminder that police can’t be complacent.

“All of law enforcement must remain diligent in its responsibility of keeping our communities safe,” State Police Director Larry Trent said in a statement. “Our goal continues to be a significant decrease in all of the reported offenses.”

The differences in results among different regions and counties were significant.

Serious crime declined in 53 Illinois counties and increased in 48 counties. Twenty-five counties had more murders than in 2005, while 17 had fewer.

Murders were down just under 1 percent in Illinois’ urban counties, even though Chicago murders increased to 467 in 2006 from 450 in 2005 – nearly 4 percent.

In rural areas murders doubled to 30 from 15, but the total was similar to totals posted in years before a big drop to 15 in 2005.

A huge population difference between urban and rural areas also skewed the statewide results. For example, murder arrests were up 116 percent in rural areas but down 20 percent in the urban counties, sending the statewide total down 16 percent from 2005.

David Olson, head of the criminal justice department at Loyola University in Chicago, said fewer murder arrests could indicate murders are becoming harder to solve, with witnesses unwilling to testify in gang shootings, for example.

Also, assaults were up 1.5 percent in rural areas but down 3.7 percent in urban counties, dropping the statewide tally by 3.1 percent from 2005.

Overall crime arrests were down similarly in both rural and urban counties, with large drops in murder, rape, auto theft and arson.

Drug arrests had grown steadily in rural areas as law enforcement battled a scourge of methamphetamine production, but that leveled off last year.

Total drug arrests were up 0.4 percent in urban areas but down 9 percent in rural counties. Police in rural areas reported a 20 percent drop in arrests for controlled substance violations and a nearly 40 percent decline in hypodermic needle arrests.

Peaks and valleys in the statistics shouldn’t be a reason for alarm or celebration, Olson said.

“One less burglary is treated the same as one less homicide,” Olson said. “You’re still very unlikely to get robbed or murdered.”

The data, covering through the end of 2006, is several months old, so police departments could already have addressed possible problem areas, Olson said.

“No one can really hold anybody accountable for what’s going on right now,” he said.