A day-long shootout between prisoners and security guards at a jail in the Central Asian republic of Kazakhstan ended with a powerful blast, leaving 17 dead, officials said on Tuesday. Sixteen prisoners died in the explosion in the southeastern town of Balkhash, the Kazakh justice ministry\'s prison system spokesman Sultan Kusetov told AFP. Kusetov also confirmed that at least one prison guard died and several were wounded in the violence. The justice ministry official described the incident as a failed prison break orchestrated by hardened criminals who each faced sentences of 15 to 32 years in jail. \"We fulfilled our main objective. Those who tried to flee (the jail) were unable to leave,\" he said. The ex-Soviet republic has been experiencing prison unrest for several years and has come under criticism from the European Union for rights abuses and other violations that have seen opponents of the authorities end up in jail. Seven Kazakh guards were last month convicted of torturing nearly 30 inmates while there have also been cases of prisoners setting themselves on fire in the country\'s more notorious jails. The justice ministry official gave contradictory accounts of what happened at the Balkhash facility and could not explain the cause of the blast that he said ultimately killed the inmates. He said a stray bullet may have hit an oxygen tank in the prison. But he added that the inmates could have blown themselves up after realising their escape attempt had failed. The violence, which lasted around 24 hours, began with a late Sunday prison break attempt, the official said. The gang briefly took several hostages and barricaded themselves in a section of the jail. Kusetov said the group of convicts included a man found guilty of \"belonging to a religious extremist organisation\" but provided few details about the other men. Kazakhstan has in the past blamed prison violence on religious extremists, but Kusetov stressed the prisoners involved had ties with organised crime and appeared to have received an arms shipment from their supporters. \"Logic tells you that they received these arms from criminal associates who helped them plot the escape,\" the Kazakh official said. \"Perhaps they blew themselves up because they did not want to give themselves up to the authorities,\" Kusetov said. \"They knew they had injured some of our staff, that they had killed one of them... They knew that there would be no mercy for them now.\" The incident was not reported by Kazakhstan\'s official state news channel and senior officials made no direct reference to it in public statements. The energy-rich republic has established a business-friendly environment that has attracted Western capital to large natural resource projects and is being encouraged by Europe to follow up with political reforms. But President Nursultan Nazarbayev came under strong criticism from international observers in April after he won re-election for a third decade in power with a reported 95 percent of the vote.