At least 20 people were killed when police clashed with Islamic militants in Chechnya's capital, Grozny, on Thursday.

The fighting began about 1 in the morning, when about 10 gunmen in three cars fired on police who had stopped them, killing three officers.

Some of the militants then holed up in a nearby office building and traded gunfire with police who quickly cordoned the area.

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The battle left the 10-story Press House, which housed local media offices, gutted by a blazing fire that also spread to a nearby street market. Some gunmen fled to an empty school nearby.

It took police more than 12 hours to kill 10 militants, according to Russian authorities, who also reported that 10 officers were killed and 28 wounded.

The new violence raised fears of more attacks in Chechnya and widening unrest throughout Russia's volatile North Caucasus region.

The Kavkaz Center Web site, a mouthpiece for Islamic militant groups operating in the North Caucasus, carried a link to a video message by an individual claiming responsibility for the attack.

The man in the video said he was operating on orders from Emir Khamzat, reportedly a nom de guerre of Chechen warlord Aslan Byutukayev. The claim could not immediately be verified.

The insurgents in Chechnya and other Caucasus regions want to create an independent state governed by their strict interpretation of Islamic law.

Some Caucasus militants have traveled to Syria and Iraq to join up with the Islamic State group, which has vowed to launch attacks in Russia.

The gunbattles were still raging when Russian President Vladimir Putin began delivering his address in the Kremlin, and the Russian leader sought to cast the violence as a legacy of what he described as foreign support for Chechnya-based insurgents in the past.

TagsChechen Attack, Islamic militants, Chechnya