The warden of a prison in the northwestern Venezuelan city of Maracaibo escaped unharmed on Thursday when a group of inmates shot at him, authorities in Zulia state said.

The prison chief came under attack while investigating a report of armed inmates in one of the cellblocks, state Security and Public Order Secretary Odalis Caldera told Efe.

The warden was accompanied by members of the police team responsible for security outside the prison walls and the attack "was repelled" without any casualties, she said.

She said a search for weapons was under way inside the penitentiary and that extra guards had been posted on the perimeter.

The Venezuelan government acknowledges "a grave problem" with weapons inside the country's vastly overcrowded prisons, but insists the matter will be addressed as part of a restructuring of the penal system.

Violence in the Andean nation's prisons claimed 304 lives in the first half of the year, an increase of 15 percent over the same period in 2011, the independent Venezuelan Prisons Observatory said Monday.

Two days later, the Prisons Ministry reported that guards confiscated 22 firearms - including a submachine gun - and two tear-gas grenades from inmates at a penitentiary in the central state of Carabobo.

Also seized were more than 2,000 bullets, three knives, three computers, 98 cell phones and 98 packets of illegal drugs, ministry official Mary Pili Viera said.

The ministry was created a year ago after a month-long standoff between army troops and nearly 1,000 armed inmates at a prison on the outskirts of Caracas. EFE