A gunman who shot dead two people in a Russian Federal Security Service (FSB) office before being killed himself was an Isis operative, the terror group has claimed.

The assailant, who has not been named by Russian authorities, also wounded a third person after he burst into the agency headquarters in Khabarovsk near the Chinese border in the far east of the country.

The gunman opened fire just outside a security checkpoint in a reception room of the office on Friday (21 April), the FSB said.

An FSB officer and a visitor were killed, the agency added.

The assailant, identified as an 18-year-old resident of Khabarovsk Region, was killed as security guards returned fire.

The FSB said the gunman belonged to an unnamed nationalist group. He had killed an instructor at a local shooting club and stole a hunting rifle and two pistols to carry out the attack.

According to Russia Today, the attacker, who was not carrying explosives, had links to a neo-Nazi group although a statement released by the Isis-linked Amaq news agency contradicted that claim.

Evidence is still being collected from the scene. Social media postings showed police cordons outside the heavily-policed building.

The FSB is the main successor organisation to the feared KGB and mainly deals with counter-terrorism and national security.

The Kremlin is still investigating a suicide bomb attack on the St Petersburg Metro which left at least 11 dead. Although Isis links to the explosion have been probed, no evidence linking them to the bombing have been made public.

The blast took place on a train between Sennaya Square and the Technological Institute. Kyrgyzstan-born Akbarzhon Jalilov, 22, was named as the assailant.

Seaparately, Moscow is reportedly mobilising troops and equipment along its 11-mile border with North Korea amid fears that US President Donald Trump could launch a strike against the hermit nation.

FSB attack
Interior Ministry officers cordon off a street outside the Khabarovsk Federal Security Service headquarters after the fatal shooting REUTERS/Reuters TV