At least 12 people, including a top local police official, have been killed by two suicide bombings in Russia's North Caucasus republic of Dagestan.

A car bomb was detonated at about 0830 (0430 GMT) outside the offices of the local interior ministry and the FSB security agency in the town of Kizlyar.

Another bomber then blew himself up 20 minutes later as a crowd gathered.

Russia is on alert after double suicide bombings on the Moscow Metro on Monday morning, which left 39 people dead.

Prime Minister Vladimir Putin has called on the security forces to "scrape from the sewers" those responsible for the Moscow attacks. Investigators say they believe the bombers were linked to militants in the North Caucasus.

At a government meeting following Wednesday's bombings in Dagestan, Mr Putin condemned the "terrorist act" and said he did "not rule out that it is one and the same gang at work".

President Dmitry Medvedev said the two sets of bombings were "links of the same chain".

A militant Islamist group led by a Chechen rebel on Wednesday denied responsibility for the blasts.

"We did not carry out the attack in Moscow, and we don't know who did it," Shemsettin Batukaev, a spokesman for the Caucasus Emirate organisation led by Doku Umarov, told Reuters by telephone in Turkey.

The spokesman added that the group had planned attacks on economic targets inside Russia, but not against civilians.

Last month, Doku Umarov warned that his fighters' "zone of military operations will be extended to the territory of Russia... the war is coming to their cities".

In Wednesday's attacks, the first bomber detonated about 200kg of explosives when police tried to stop his car as he drove into the centre of Kizlyar, Dagestani Interior Minister Rashid Nurgaliyev said.

"Traffic police followed the car and almost caught up - at that time the blast hit," he told local television.

As police, emergency services personnel and residents gathered at the scene, a suicide bomber wearing a police uniform approached and blew himself up, killing among others the town's chief of police, Col Vitaly Vedernikov, Mr Nurgaliyev added.

Mobile phone footage posted on the internet afterwards showed the moment of the second blast, with officials walking past a damaged building before a loud bang rings out and smoke rises in the distance.

A total of nine police officers were among the dead, the investigative committee of Russian prosecutors said in a statement. Twenty-three people were injured.

Mr Nurgaliyev later ordered police to increase security at official buildings across the republic, as well as at places where crowds gather, including schools, colleges and cinemas.

Dagestani President Magomedsalam Magomedov said the explosions in Moscow and Kizlyar were linked and he vowed to "eliminate" the perpetrators, Russia's Interfax news agency reported.

Kizlyar is close to Dagestan's border with Chechnya, where Russian forces have fought two wars against separatists since 1994 that claimed more than 100,000 lives and left the republic in ruins.

Chechnya has in recent years been more peaceful, but the fighting has spread to Dagestan and Ingushetia, where a violent Islamist insurgency is growing.

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