A 17-year-old student has blown himself up in the lobby of Russia's Federal Security Service (FSB) in the northen city of Arkhangelsk, injuring three employees. The unnamed teenager detonated a homemade explosive device at about 09:00 local time (06:00 GMT) on Wednesday and died on the spot, the country's Investigative Committee said in a statement. She said checks would also be carried out to establish whether he was a member of any banned group. Regional governor Igor Orlov said that the authorities were working to establish the type of explosive used. "Things are very serious," he said. "We are taking measures to increase security of all public and state buildings in Arkhangelsk region." Seven minutes before the blast, a post in an anarchist forum on Telegram, a messaging service, warned that the FSB building would be the target of a "terror attack". The writer of the post, who signed as Valeryan Panov, said he would claim responsibility for it.