MURMANSK - A blast hit an office of the Russian Federal Security Service (FSB) in the northwestern city of Arkhangelsk on Wednesday, leaving three people injured and the attacker dead.

The explosion occurred at the very beginning of the working day, with the first photos from the site emerging almost immediately after the incident.

The area around the attack was promptly cordoned off.

The governor of the Arkhangelsk Region, Igor Orlov, called an emergency meeting of the regional government, after which he made an official statement.

"Three people are in a hospital and one was killed. His identity is being determined," the governor said.

According to the official, the blast went off inside the entrance of the FSB building.

Less than three hours after the explosion, the National Anti-Terrorist Committee (NAC) said that the attack was staged by a 17-year-old male, who died in the blast.

"According to preliminary data, a 17-year-old local resident, who brought an improvised explosive device into the building, has died as result of the incident.

Three employees of the regional department of the Federal Security Service were injured in the explosion. Investigators and criminal experts of the Russian Investigative Committee are working at the site. Eyewitnesses are being questioned, and relevant procedures have been launched," the Investigative Committee said later in a statement.

Russia's Investigative Committee head Alexander Bastrykin asked the investigators to find out motives of the attacker as well as determine his circle of contacts.

In another statement, the investigative committee said that the incident was being regarded as a terrorist attack.

"In Arkhangelsk, a criminal case was initiated under Article 205 of the Criminal Code of the Russian Federation (terrorist act) and Part 1 of Article 222 of the Criminal Code of the Russian Federation (illegal possession of ammunition) in connection to the explosion in the FSB regional department building," the committee said in the statement published on its WhatsApp channel.

The Investigative Committee issued in its WhatsApp channel a photo of the 17-year-old suspect. The photo shows the teenager wearing a jacket and a backpack.

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Some media reported that the teenager was allegedly a student of the Arkhangelsk Polytechnic College. The college has not commented on this information.

"Sorry, we are not providing any data," a representative of the college said.

Social networks have also spread reports that the teenager had allegedly given warnings about his intention to stage an explosion in the FSB building.

The Arkhangelsk region's children ombudsman, Olga Smirnova, announced her plans to cooperate with investigators on the issue in order to find out more details about the attacker.

According to Orlov, security measures in all of the region's public places have been improved.

"The authorities took all the necessary measures to ensure the operation [of all public institutions] after the incident. We took measures to boost the security systems of all public and state institutions of the region," Orlov told reporters.

Mayor of Arkhangelsk Igor Godzish said that access to administrative buildings, cultural centers and educational institutions had been restricted.

"I call on the local residents to show us their understanding for the measures aimed at enhancing security and temporary public transport routes in connection with the closure of Troitsky Avenue, as well as be vigilant and show civil responsibility," Godzish added.

This was the second attack staged by a teenager in Russia this month. On October 17, Vladislav Roslyakov, 18, carried out a shooting and bombing attack at the Kerch polytechnic college, where he was a fourth-year student. According to official data, 21 people were killed, including 16 students and 5 staff members, and nearly 50 more were injured. The attacker also died in the attack, and his motives still remain unclear.