Russia's Federal Security Service said on Friday that a gunman had burst into one of its regional offices in the far east of the country and opened fire, killing one of its employees and a visitor.The region where the incident happened is close to China. The FSB, the successor organization to the Soviet KGB, said the attacker had been killed and that another person had been injured in the incident."An unknown person entered the reception of the FSB's Khabarovsk regional branch and started shooting at people inside," the FSB said in a statement.The Site Intelligence Group, a US-based monitoring service, said that Islamic State had claimed responsibility for the attack. It said that the claim of responsibility had been made through the militant group's Amaq news agency.That contradicted earlier media reports, which said the FSB believed the gunman was a nationalist. The TASS news agency cited an unnamed FSB official as saying that the gunman was a local resident and born in 1999.The visitor who was killed and the one who was injured were from former Soviet states outside Russia, according to the security service.Russia was this month shaken by a suicide bombing of the St Petersburg metro, which killed 16 people. The suspected suicide bomber and his alleged accomplices were from Central Asia.The man Russian police believe was the suicide bomber had developed an interest in Islam and soon after traveled to Turkey, two people who knew him told Reuters.