Update as of 12:50 a.m. EST: At least six militants, reportedly trapped in a building in central Grozny, have been killed by police, Ramzan Kadyrov, head of the Chechen Republic, announced on his Instagram page Thursday. Sputnik confirmed the authenticity of the post.

“The operation to destroy the bandits is entering its final phase. Six terrorists have already been eliminated in the Press House,” he wrote.

At least three police officers were killed in overnight clashes with gunmen in the capital of the conflict-ridden Chechen Republic. According to a report by TASS, a Russian state-owned news agency, the incident happened when unidentified gunmen opened fire after their car was stopped by security officials in central Grozny.

The Russian National Anti-terrorist Committee said that after the shooting, the “militants” had stormed a building housing a local media agency, which has since been surrounded by law enforcement officials, according to a report by Sputnik news. Interfax, another Russian news agency, reported, citing Chechen government officials, that there were five or six militants trapped in the building in central Grozny.

“According to our data, there are five or six members of an illegal armed group … measures are being taken to neutralize them,” the interior ministry of the Chechen Republic reportedly said, in a statement.

Ramzan Kadyrov, head of the Chechen Republic, also confirmed that an attack had taken place, according to local media reports. He, however, reportedly termed the incident a minor one and dismissed reports that a large number of militants had entered the city.

“The situation is completely calm, cars are going around the city … all the talk about the city being under the control of militants is absolutely false,” he reportedly said. “I ask residents in areas where (security) operations are being carried out to abide by safety measures and not to go out onto the streets without cause or to go near their windows.”

The attack, which comes just days before the 20th anniversary of the First Chechen War, marks an end to a period of relative calm in the region. Separatists in Chechnya, a Muslim-dominated region, have fought two wars with Russia since the break-up of the Soviet Union in 1991.

However, in recent years, following a military krackdown led by the Russia-backed Kadyrov -- who has been accused of widespread human rights abuses -- a fragile peace has prevailed in the region.