Inmates of Venezuela's blocked more than 680 people who came to visit their relatives in the premises of the Los Teques prison, the Globovision channel reported on Sunday.
The inmates said the people will not leave the building until their demands are met. Their demands were not immediately known.
The prisoners say the incident was to show support to inmates in Yare-1 and Yare-2 prisons, where about a thousand people, mostly women and children, refused to leave the building in protest against alleged abuses and delays in sentencing of their jailed relatives.
A total of 487 people died in Venezuelan jails in January-October 2011. The total number of deaths in the country's notoriously violent and overcrowded prisons has topped 4,500 in 1999-2010.