4 Dead in Counterterrorism Raid in St. Petersburg, Russia

MOSCOW— -- Russian security forces said they killed four suspected militants today when they stormed an apartment in St. Petersburg during a counterterrorism raid.

Heavily armed officers were met with gunfire as they tried to enter the apartment on Leninskii Prospekt in the city's suburbs, according to a statement from Russia's Investigative Committee.

The Committee, Russia's equivalent of the FBI, said the raid was carried out in an effort to arrest suspected members of terrorist groups from the North Caucasus, a region home to a long-running jihadist insurgency. The suspects were killed when officers returned fire, the statement said.

Beginning mid-morning, posts on social media and reports in local news outlets showed around two dozen police in helmets and body armor surrounding the apartment block. Police cordoned off the building, refusing to allow people outside. Witnesses told the Interfax news agency they had heard shots, as well as loud booms that made the walls of the building vibrate.

The Russian news agency RIA Novosti initially reported that three of the suspects may have been detained, citing security service sources, but the Investigative Committee statement clarified they had been killed in the shootout.

Investigators were examining the apartment and working to establish the identities of those killed, it said. A criminal investigation has been opened around possession of firearms and explosives.

Russia is on high alert for terror attacks. After the country’s military intervention in Syria, the Islamic State promised to retaliate with attacks on Russian soil. In recent months, Russia’s FSB security service has said it has foiled a number of terror plots linked to ISIS, arresting groups it alleged were planning attacks similar to those that struck Paris last November. Most of those arrested are reportedly from Central Asian countries.

In recent weeks, Russian security services have been conducting anti-terrorism operations at an increased tempo in the North Caucasus, where Moscow has been battling jihadist militant groups for well over a decade. In June, police in Dagestan said at least four officers and six militants had been killed in clashes.

In the 2000s, militants linked to groups in Chechnya and Dagestan staged bloody terrorist attacks across Russia, targeting civilians in retaliation for Moscow's military operations in Chechnya. Although the number and scale of terrorist incidents have since fallen significantly, groups in the region linked to al Qaeda, and now recently ISIS, have pledged to stage attacks.