CARACAS, Venezuela (AP) — The number of killings inside Venezuela's prisons has increased this year even as President Hugo Chavez faces mounting pressure to curtail the violence as the socialist leader campaigns for re-election.

The Venezuelan Prisons Observatory, a watchdog group that tracks prison violence, says that more than 300 inmates were killed in riots and violent clashes between rival gangs in Venezuelan prisons during the first half of 2012, a 15 percent increase compared to the same period last year.

The organization's director, Humberto Prado, said Monday that 304 inmates have been slain and 527 prisoners suffered injuries from January through June.

The group says about 560 inmates were killed last year.

Deadly violence and overcrowding within prisons have become major problems for Chavez's government.