“Members of illegal armed groups opened fire at soldiers, killing two, when they were uncovered through a special operation,” the Investigative Committee said in a statement.

Two other soldiers serving with the interior ministry were wounded in the same area and hospitalised on Tuesday, it said.

In a separate attack, gunmen also killed a policeman in Dagestan’s capital Makhachkala, regional police said.

Police major Yarakhmed Osmanov was on duty in Makhachkala Tuesday when several people fired at him, the regional interior ministry said in a statement.

He sustained multiple gunshot wounds and “died without gaining consciousness,” the ministry said. A passer-by was also sent to the hospital with a wound to his leg.

Also on Wednesday, security officers disarmed a bomb planted in a car near the central market in Khasavyurt, another city in Dagestan.

A one-metre (three-foot) long metal pipe was turned into a makeshift explosive and placed in the back of the car, the National Anti-Terror Committee said in a statement.

The bomb had a strength of 100 kilogrammes of TNT equivalent, it said.

Dagestan has been by far the most affected by an Islamist insurgency in recent months, with killings of policemen, government officials, and religious leaders occurring on a near daily basis.

“Despite the measures taken by security forces and officials, the situation in the region continues to be difficult,” the interior ministry said Wednesday in a message to Dagestan residents.

The ministry asked locals to report “suspicious actions” of neighbours and friends and promising anonymity and financial reward.

The Kremlin has been fighting insurgents in the North Caucasus since the 1991 collapse of the Soviet Union, waging two wars against separatists there.

Although the second war ended in 2000, the unrest has increasingly been spreading across the Caucasus.