"More than 20 prisoners were killed after special operations this morning," a prison administration official told AFP, speaking on condition of anonymity.

"The situation in the prisons remains difficult," the official added.

The riots were sparked by an attempt to move around 25 inmates led by criminal kingpin Aziz Batukayev out of Moldovanovka jail near Bishkek where a lawmaker was killed last month during a visit in clashes between inmates and prison guards, officials said.

"There was an attempt to move several criminal gang leaders, including Aziz Batukayev, into quieter prisons and search all the prisoners," said the official.

The death toll was substantiated by human rights campaigners.

"More than 20 inmates died when prison 31 was stormed, and several prisoners are injured," said Aziza Abdrasulova, a human rights activist, referring to the Moldovanovka facility.

Riots occurred at Petrovka, Moldovanovka, Novo-Pokrovka and Jalal-Abad jails around Kyrgyzstan as inmates communicated by mobile phones to coordinate the protest, another official from Moldovanovka jail said.