AT LEAST 20 people have died following attacks by suspected Islamist militants on houses of worship in co-ordinated actions in two cities in Russia’s southern region of Dagestan.

The first of three days of mourning began yesterday as the death count rose following the rampage in the regional capital of Makhachkala and nearby Derbent on Sunday evening.

Although there was no immediate claim of responsibility, the attack was the latest blamed on Islamist extremists in the predominantly Muslim region in the North Caucasus, and the deadliest in Russia since March when gunmen opened fire at a concert in suburban Moscow.

The Isis affiliate in Afghanistan that claimed responsibility for March’s raid quickly praised the latest attack, saying it was conducted by “brothers in the Caucasus who showed that they are still strong.”

The US-based Institute for the Study of War said that Isis’s North Caucasus branch, Vilayat Kavkaz, likely was behind the attack, describing it as “complex and co-ordinated.”

Dagestan Governor Sergei Melikov blamed members of Islamist “sleeper cells” directed from abroad but did not give any other details.

He said in a video statement that the assailants aimed at “sowing panic and fear” and attempted to link the attack to Moscow’s military action in Ukraine, but also provided no evidence.

President Vladimir Putin had sought to blame the March attack on Ukraine.

A Kremlin spokesman said Mr Putin has received reports on Sunday’s attacks and efforts to help the victims, but the president did not immediately comment.

The Investigative Committee, the country’s top state criminal investigation agency, said all five attackers were killed.

Of the 20 people killed, at least 15 were police.

Reverend Nikolai Kotelnikov, a 66-year-old Russian Orthodox priest at a church in Derbent was among those killed.

The attackers slit his throat before setting fire to the church, according to a local public oversight body.

The attack came as Pentecost, also known as Trinity Sunday, was being celebrated.

The Kele-Numaz synagogue in Derbent also was set ablaze.

Militants then fired at a police post in Makhachkala and attacked a Russian Orthodox church and a synagogue there before being hunted down and killed by special forces.

In the early 2000s, Dagestan saw near-daily attacks on police and other authorities that were blamed on militant extremists.