Ten police officers have been killed in clashes with fighters who attacked a traffic post in the Chechen capital Grozny, and then stormed a building housing local media, Russian officials said.
Ten attackers were also killed in Thursday's attack, Russia's National Anti-terrorism Committee (NAK) said, adding that another 28 law enforcement personnel had been wounded.
The bloodiest fighting in Chechnya for months erupted a few hours before President Vladimir Putin said in a speech in Moscow he would defend Russia against what he called attempts to dismember it.
"There are unconfirmed reports that the attacks were carried by Islamist fighters," Al Jazeera's Peter Sharp reported from Moscow.
- The Kremlin fought two wars with separatists in Chechnya
- The first: from 1994 to 1996
- The second: from 1999 to 2009
- At least 160,000 people were killed in the two wars
- In October, five policemen were killed in suicide attack
NAK said a group of assailants attacked a traffic post in Grozny in the early hours of Thursday and then stormed a building housing local media known as the Press House.
In the evening, the committee said its "anti-terrorist" operation was over and all suspects killed.
Putin praised the Kremlin-backed leader of Chechnya, Ramzan Kadyrov, for carrying out a "professional" security operation.
He also alleged that the attack had been planned from abroad.
"We remember well who and how in the 1990s supported separatism, and even terror in our lands, by calling murderers with their hands soaked in blood simply rebels," he said.
"These decisions were made at the highest levels. Well, the same rebels have now showed up in Chechnya."
Five policemen were killed and a dozen wounded in Grozny in October when they stopped a young suicide bomber from attacking a concert hall where thousands had gathered to mark a local holiday.
That blast, which shattered a period of relative calm in the region, sparked concerns of a new cycle of violence in the North Caucasus where the Kremlin has fought two wars with separatists over the past 20 years.
Putin has staked his political career on a promise to crush the bloody insurgency in the Caucasus.
When Putin turned 62 on October 7, more than 100,000 people, decked out in the colours of the Russian flag, marched in Grozny, led by Kremlin-backed regional leader Ramzan Kadyrov who carried a portrait of the Russian president.
About 1,100 guests including top officials and lawmakers will attend Putin's address to the nation which is expected to lay out Kremlin's political and economic priorities during a bitter confrontation with the West over Ukraine.
Source: Al Jazeera and agencies