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, the minister, Bacho Akhalaia, said in comments on the ministry website.
"This is why I have submitted my resignation to the president."
The abuse videos shocked the nation and drew international condemnation, causing protesters across the ex-Soviet state to call for the resignation of Akhalaia, who served as prisons chief from 2005 to 2008 and was accused by critics of violating human rights.
The interior minister's resignation follows that of the prisons minister on Wednesday, and was greeted by cheers from jubilant protesters in central Tbilisi.
"We are happy that he resigned but it is not enough, he must be arrested," one protester, Tamar Robakidze, told AFP after Akhalaia quit.
"We've been disappointed by this government for a long time but what we have seen recently is beyond any limits," said another, Tsotne Nakashidze.
One of the graphic videos that caused the scandal 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.
Opposition channel TV9 late Thursday aired a new but heavily-pixellated video of what it claimed were guards assaulting an inmate in a detention centre for people with mental disorders.
The scandal erupted as 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.
Several thousand people demonstrated for a second day Thursday in Tbilisi and the cities of Batumi and Rustavi to vent their anger.
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".
At another protest outside the 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, President Saakashvili on Thursday appointed human rights ombudsman Giorgi Tugushi as the new prisons minister.
"Giorgi Tugushi has been a very strong critic of the (penitentiary) system and I am appointing the system's harshest critic as its leader," Saakashvili said on live television.
Tugushi pledged: "My priority will be a complete overhaul of the system."
In another measure aimed at tackling the abuse crisis, Saakashvili had on Wednesday deployed police in jails to replace prison officers, while government officials also vowed to eradicate torture.
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.
EU foreign policy chief Catherine Ashton, adding her voice to the international outcry, said in a statement that she was "appalled by the shocking footage of abuses committed against inmates".
Ashton called for a transparent investigation, saying that "all countries are obliged to comply with the unconditional prohibition of any form of torture and ill-treatment".
Akhalaia's deputy Eka Zguladze has been promoted to acting minister after his resignation, she said in a statement on the ministry's website.