Kyrgyzstan's president has ordered an inquiry after a member of parliament and at least two others were killed by inmates during a prison visit.
Tynchbek Akmatbayev was said to be in prison to inspect conditions
Tynchbek Akmatbayev was shot dead after being taken hostage during a visit to Moldavanovka prison, about 25km (15 miles) outside the capital, Bishkek.
The others who died are said to have been members of his entourage. Prison service head Imatulla Polotov was hurt.
The killings come after two days of unrest at nearby Novopokrovka prison.
Inmates there have been protesting about bad food, damp accommodation, inadequate clothing and a lack of hot water.
Mr Akmatbayev, a prominent MP, was chairman of a parliamentary committee on security and policing.
He had been involved in negotiations with prisoners at Novopokrovka, about 20km (12 miles) east of Bishkek, where inmates were said to have forced prison officers outside the building.
He and his entourage were in the tuberculosis hospital attached to Moldavanovka prison on a visit to assess living conditions when they were taken hostage.
The Kyrgyz government press service has quoted eyewitness accounts which suggest the MP's party was the first to open fire.
"Akmatbayev was shot dead," said Sergei Sidorov, spokesman for the sentencing board.
Mr Polotov was severely beaten but survived, a spokesman from the Justice Ministry said.
Prime Minister Felix Kulov is reported to have gone to the prison and successfully negotiated the release of Mr Akmatbayev's body.
President Kurmanbek Bakiev ordered the investigation into the deaths after discussions with Mr Kulov and law enforcement officials.
Reports say prison guards have left the jail and taken up positions outside, leaving it in full control of the approximately 450 inmates.
Officials have not said how the inmates acquired firearms. However, at least one member of Mr Akmatbayev's entourage was armed, according to witnesses.
An official said the situation at the other prison in Novopokrovka was now calm.
Kyrgyzstan has witnessed several violent incidents since the overthrow of ex-President Askar Akayev in March.