Russian authorities said on Sunday they had brought a siege at a prison in the southern Rostov region to a swift end, killing the hostage-takers from the militant Islamic State (IS) group and freeing their two prison guard captives unharmed.

The prison service had earlier reported that the two guards had been taken hostage by an unspecified number of IS detainees and had entered negotiations for their release.

But a short time later it issued a statement saying the siege had ended: “During a special operation…the criminals were liquidated and the employees who were taken hostage were released and were not injured.”

No further details were released in the immediate aftermath of the drama at Detention Centre 1 in the Rostov region.

A police source told state news agency TASS that IS members who were due to appear in court on terrorism charges were among the hostage-takers.

They were reported to be holed up in the prison courtyard, armed with a pocket-knife, a baton and an axe, the source said.

The Interfax news agency said there were six hostage-takers who demanded to be provided with a car and be allowed to leave the prison in exchange for the release of the hostages.

The incident comes nearly three months after gunmen killed at least 144 people when they opened fire inside a concert hall near Moscow in an attack claimed by the group.

Hundreds more were injured in the March 22 attack at the Crocus City Hall, the deadliest on Russian soil for two decades.

More than 20 people have since been arrested, including the four suspected gunmen, all from the former Soviet republic of Tajikistan, an impoverished country on Afghanistan’s northern border.

Russia has been repeatedly targeted by attacks claimed by IS militants, though the jihadist group’s influence in the country remains limited.

Russian media reports speculated that the attackers at the Rostov detention centre could be among those arrested in 2022 for allegedly planning an attack on the Supreme Court of Karachay-Cherkessia, a Muslim-majority Russian republic in the Caucasus.

Nearly 4,500 Russians, mainly from the Caucasus, travelled to Iraq and Syria to fight with IS, according to official figures.

In April, two armed men who authorities said were members of “an international terrorist organisation” were shot dead by Russian forces near Nalchik in the Caucasus.