Twelve killed by twin bombings in Russia's Dagestan
Mobile phone footage shows the moment of the second blast
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.
First funerals of some of the victims took place on Wednesday.
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.
Yet another terrorist act has been committed. I do not rule out that it is one and the same gang at work
Russian Prime Minister Vladimir Putin
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".
The BBC's Richard Galpin in Moscow says that although no-one has yet claimed responsibility for either of this week's attacks, both bear the hallmarks of previous suicide bombings carried out by Islamist militants from the North Caucasus.
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.
Sarah Rainsford BBC News, Moscow
First Moscow, now Dagestan. President Dmitry Medvedev has described the attacks as "links in the same chain" - one which leads to an ongoing Islamist insurgency in the North Caucasus.
The Moscow Metro bombings were the first attacks in the Russian capital in six years. In the North Caucasus, though, suicide bombings by Islamist militants are increasingly common - and police and local government officials are the usual target.
A recent report says more than 900 people died in violence in the region last year alone, which included 15 suicide attacks.
"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.
Correspondents say poverty, unemployment and the brutal tactics of the security forces have been factors in driving young men into the ranks of Islamist rebel groups, which want to drive the Russians out.
President Medvedev recently said separatists had spread through the North Caucasus "like a cancerous tumour" and earlier this year appointed a deputy prime minister to oversee the troubled region.
He told security officials on Tuesday that the militants' goal was the "destabilisation of the situation in the country, the destruction of civil society, and to sow fear and panic among the population".
On Tuesday, Russians observed a day of mourning for those killed in the suicide bombings on Moscow's Metro, carried out by two women said to have links to the North Caucasus.
Families of the Moscow victims have been expressing anger at their loss
The first bomb tore through a carriage of a train at Lubyanka station - beneath the headquarters of the Federal Security Service (FSB) - as it stood waiting for commuters during the morning rush hour.
The second explosion, six stops away at Park Kultury, was about 40 minutes later. It hit the back of the train as people got on.
The co-ordinated attacks were the deadliest in Moscow since February 2004.
Russian media reports are linking them to the death earlier this month of a rebel leader from Ingushetia - Alexander Tikhomirov, also known as Said Buryatskiy - who was blamed for an attack on a train from Moscow to St Petersburg last year that killed 26 people.
The newspaper Kommersant quoted security sources as saying they believed Tikhomirov had recruited 30 potential suicide attackers, and that two of them might have avenged his death.
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