A tense calm returned Monday to the area following gun battles between Russian security and Islamic militants.

“According to security forces information, the neutralized militants recently swore allegiance and became part of the Islamic State worldwide terrorist organization”, the committee said.

Local media reported that Russian troops seized explosives, weapons and over 2,000 rounds of ammunition in the operation.

The agency said those killed included the group’s leader, Adam Tagilov, who was accused of staging December’s attack in Chechnya’s provincial capital, Grozny, which left 25 people dead. It also said the process of identifying those killed was still continuing.

The upper floors of the Press House was engulfed in flames and later shootings continued around a school, though no students or teachers were present at the time.

Earlier this year, several regional commanders of Russia’s Caucasus Emirate, an armed group that has sought to establish Shariah law in Russia’s predominantly Muslim North Caucasus regions, pledged allegiance to Islamic State and its leader, Abu Bakr al-Baghdadi.

That fighting broke out hours before Russian President Vladimir Putin was due to give his annual state of the nation speech and put in question the authority of Ramzan Kadyrov, the Kremlin-appointed strong-arm head of Chechnya.

They were allegedly responsible for a series of deadly attacks against police in the region. They knew some of their son’s friends had previously joined the Islamic State, the report said.