More than six hours after fighting broke out in the Chechen capital of Grozny in the early hours of Thursday, leader Ramzan Kadyrov said a multi-story publishing house building had been destroyed by fire and six gunmen killed.

The Moscow-based National Anti-Terrorist Committee said the fighters had occupied the building after killing three police officers at a checkpoint shortly after midnight, local time.

According to the state news agency RIA-Novosti, five police officers and others were injured in the clash.

Kadyrov has been widely denounced for human rights abuses, including the killing of political opponents. He has also imposed Islamic restrictions, such as the mandatory wearing of headscarves for women in public.

After a war between Moscow and separatists in the 1990s, the republic is still plagued by a Muslim insurgency and sporadic fighting in the mountains and southern regions. In October, five police officers were also killed in a suicide bombing in Grozny.

The violence in Russia's North Caucasus republic of Chechnya came just hours before President Vladimir Putin was due to deliver his annual address to the nation.

ksb/tj (dpa, AFP)