CARACAS, Venezuela — Venezuela's government started posting National Guard troops on buses Wednesday to try to prevent violent crime.

About 500 Guardsmen have been assigned to ride on buses in Caracas as a deterrent against frequent armed robberies and killings of bus drivers, Gen. Alirio Ramirez told the state-run Bolivarian News Agency. Some will escort buses by motorcycle through crime-prone areas.

President Hugo Chavez announced the idea on his Sunday television and radio program, but it wasn't clear if the project would be permanent.

Polls regularly show that crime is Venezuelans' leading concern — above unemployment and inflation.

The government reported 9,402 homicides in Venezuela for 2005, but it has not provided full-year figures for either 2006 or 2007.

Venezuelan criminologist Fermin Marmol Leon said the best estimate of murders in the country last year is about 13,000, based on tallies in Venezuelan newspaper reports.

Justice Minister Ramon Rodriguez Chacin on Tuesday disputed claims that crime has risen, saying Venezuela has averaged 152 homicides a week in recent months — "much less than the figure last year," he added, without giving details.

Caracas averages about 40 homicides per week, Rodriguez Chacin said. The Venezuelan capital has long been considered one of the most violent cities in Latin America.

The National Guard deployed more than 1,000 troops in the streets of Caracas to help deter crime in October, but they were apparently withdrawn later.

Marmol Leon said putting soldiers on buses will help in some areas, but it "doesn't solve the crime problem," noting that taxi drivers, other motorists and homeowners will still face risks.