A Russian army veteran killed two people and injured four more -- including a 10-year-old girl -- in a shooting inside a public services office in Moscow on Tuesday, city authorities and media reports said.

Russian news agencies reported that the shooter, who they identified as a 45-year-old former serviceman, believed the coronavirus pandemic to be a conspiracy theory and had refused to put on a mask.

Mayor Sergei Sobyanin called the incident a "tragedy" and confirmed two people were killed by the gunman, who had been detained.

Deputy Mayor Anastasia Rakova said two employees of the public services centre -- "an administrator and a security guard" -- were killed in the shooting in southeastern Moscow.

She said four people were injured, including the girl.

Doctors said the child had been wounded in the neck, and that she had undergone a successful operation. Three wounded adults were also operated on, authorities said.

The incident took place at a multi-functional government office that deals with a variety of administrative issues.

Rakova said the Ryazansky Public Offices Centre's staff and visitors were "immediately" evacuated when the shooting started at around 3:00 pm Moscow time (1200 GMT).

In a statement, the interior ministry said the man entered the centre "and started firing at the citizens there, after which he tried to hide".

A law enforcement officer who was at the scene "managed to catch and neutralise the attacker," the ministry added.

Policeman Georgy Domolayev told national television that he ran after the shooter, who he said had a gun and knife attached to his waist.

Officials have not yet revealed the motiviation for Tuesday's shooting
Officials have not yet revealed the motiviation for Tuesday's shooting AFP / Dimitar DILKOFF

Several Russian news agencies, citing law enforcement sources, said the gunman believed the coronavirus pandemic to be a conspiracy and that he began behaving aggressively after being told to put a mask on.

"He spoke about coronavirus and about a worldwide conspiracy," state news agency RIA Novosti cited a source as saying.

The shooter will undergo a psychiatric examination.

Russia's Investigative Committee, which probes major crimes, launched a criminal probe into the shooting.

In a statement, investigators said a man had entered a room in the government-run building and "opened fire with a firearm on the people who were in the room".

"Two people died on the spot from their injuries," the statement said.

Mass shootings in Russia are relatively rare.

The country was rocked this year by two separate tragic killing sprees -- one at a school, another at a university -- spurring lawmakers to tighten laws regulating access to guns.

Authorities have blamed foreign influence for school shootings, saying young Russians have been exposed online and on television to gun attacks in the United States and elsewhere.

In one high-profile public shooting in 2019, a gunman opened fire near the FSB domestic intelligence agency headquarters in central Moscow, killing an officer and wounding five people.

Other high-profile shooting cases have taken place in Russia's army.

In November 2020, a 20-year-old soldier killed three fellow servicemen at a military base near the city of Voronezh south of Moscow.

In a similar attack in 2019, a young recruit shot dead eight servicemen.