Georgia's interior minister resigned Thursday after the release of videos this week showing the torture and rape of prison inmates sparked fury and a wave of nationwide protests.
It was the second ministerial scalp claimed by the abuse scandal, which has hit the government of President Mikheil Saakashvili ahead of crucial parliamentary polls at the start of next month.
"I feel moral and political responsibility that we failed to eradicate the horrible practice" of torture, said the minister, Bacho Akhalaia, in comments on the ministry website.
"This is why I have submitted my resignation to the president."
Mr. Akhalaia's resignation follows that of the prisons minister on Wednesday.
The abuse videos shocked the nation and drew international condemnation, and protesters across the ex-Soviet state had called for the resignation of Mr. Akhalaia, who served as prisons chief from 2005 to 2008.
One of the graphic videos showed a weeping half-naked male prisoner in a Tbilisi jail begging for mercy before apparently being raped with a stick. Other footage showed prison guards brutally kicking an inmate.
Several thousand people demonstrated for a second day Thursday in Tbilisi and the cities of Batumi and Rustavi to vent their anger.
Around 1,000 people marched through Tbilisi to the presidential palace and to the prosecutor's office, some carrying placards with messages that read "Don't torture" and "Don't tolerate, investigate."
About 1,000 protesters gathered outside the Tbilisi state concert hall.
One woman held up a picture of her brother, who she said had been killed in jail. "There is no justice in Georgia," the woman, Manana Abuselidze, told AFP. "I am not alone, there are more dead youngsters like him."
Demonstrators also rallied in the Black Sea port city of Batumi, and furious protesters outside a jail in Rustavi banged their fists on prison vans and jostled the chief guard.
In an attempt to calm the outrage, Mr. Saakashvili on Thursday appointed human rights ombudsman Giorgi Tugushi – whom he described as the prison system's "harshest critic" – as the new prisons minister.
The prosecutor's office said that 11 prison officials had been arrested and that authorities were searching for another. It alleged that some of the suspects had been paid a "significant sum of money" to carry out "inhuman and degrading treatment and torture" and then to deliver the films to an unnamed mastermind.
The scandal erupted as Mr. Saakashvili's party faces a major challenge in the October 1 parliamentary polls from an opposition bloc led by billionaire tycoon Bidzina Ivanishvili, who has vowed to oust the government.
Surveys conducted before the scandal erupted showed Mr. Saakashvili's party some 20 points ahead of Georgian Dream, a platform set up by Mr. Ivanishvili.
Mr. Saakashvili became the West's darling when he rose to power after the bloodless "rose revolution" that toppled Eduard Shevardnadze in 2003.
But opponents have accused him of curbing political freedoms and criticized for leading Georgia into a brief but disastrous war with Russia in August, 2008.