Russian special forces freed two prison guards and shot dead six inmates linked to the Islamic State militant group who had taken them hostage at a detention centre in the southern city of Rostov on Sunday, Russian media said.

State media said that some of the men had been convicted of terrorism offences and were accused of affiliation with the Islamic State militant group, which claimed responsibility for a deadly attack on a Moscow concert hall in March.

"During the special operation to free the hostages in pre-trial detention center No. 1 of the Federal Penitentiary Service of Russia in the Rostov region, the criminals have been eliminated, the employees who were held hostage have been released and they are safe," the Federal Penitentiary Service of Russia for the Rostov region told TASS.

A few hours earlier, the prison administration had said that two guards had been held by prisoners in detention centre No. 1 in the Rostov region, Russia's gateway to the Caucasus.

According to a security source interviewed by the state news agency TASS, the hostage-takers included members of ISIS who were due to appear in court on charges of "terrorism".

According to the same source, the attackers had hidden in the courtyard of the detention centre with a penknife, a baton and an axe.

According to Interfax, the attackers demanded that they be provided with a car and allowed to leave the detention centre in exchange for the release of the hostages.

Russia has repeatedly been the target of attacks claimed by ISIS.

On 22 March, gunmen opened fire at a concert hall near Moscow, killing at least 144 people and wounding hundreds more. It was the deadliest attack on Russian soil since 2004.

Since then, more than 20 people have been arrested, including four attackers, all allegedly from Tajikistan, a former Soviet republic in Central Asia bordering Afghanistan. ISIS soon claimed responsibility for the attack.