More than an inmate a day were killed in Venezuela's crowded prisons last year, as riots and weapons trafficking ran rampant behind bars, a human rights group said in an annual report on Wednesday. Some 498 Venezuelan prisoners were killed in riots and other violent acts in 2007, up from 412 in 2006, according to the Venezuelan Observatory of Prisons, the leading prison watchdog in Venezuela. The group has monitored jail conditions in the country for more than five years and conducts regular prison visits. So far this year, at least 15 prisoners have died, the group's director, Humberto Prado, told a news conference called to present the report - complete with photos of mutilated prisoners' bodies. Prado blamed the killings largely on arms trafficking inside prison. Officials seized 3,825 weapons, including 3,000 knives and 200 pistols, in Venezuelan jails last year, he said. The government didn't comment publicly on Wednesday's report. But in his recent state of the nation address, Chavez said the government needs to focus more attention on improving poor prison conditions.