The bomb caused major damage to the police station building
At least 20 people have been killed by a bomb at a police station in Russia's southern republic of Ingushetia.
The suicide attack in Nazran, Ingushetia's main city, injured more than 138 people, including children.
The republic borders Chechnya and has seen a spate of shootings, bombings and other attacks on police and government.
Ingushetia's leader blamed militants, but Russian President Dmitry Medvedev sacked the region's interior minister, saying the attack had been preventable.
"This act of terror could have been averted," Mr Medvedev said. "The police must protect the people and the police must also be able to defend themselves."
Monday's bomb attack was the deadliest strike in Ingushetia since 2004, when some 90 people were killed when hundreds of gunmen staged a raid on the centre of Nazran.
Sarah Rainsford, BBC News
This attack is part of a recent surge in violence in the mainly Muslim North Caucasus region of Russia. The large-scale separatist conflict that ravaged Chechnya has now ended after 15 years. In April, the Russian president declared Chechnya to be stable enough to ease security restrictions, and lower the number of Russian troops.
But the insurgency in the Caucasus has gradually changed form into an Islamist uprising, and spread beyond Chechnya's borders. Militants have targeted government officials and the security forces in particular, with a combination of deadly gun battles and suicide attacks.
President Yunus-Bek Yevkurov was appointed by the Kremlin to head the autonomous republic of Ingushetia - and arrived vowing to end the violence and combat serious corruption. He's still recovering from an attempt on his life.
Images from the scene showed devastation within the compound and a 4m (13ft) wide crater. Nearby homes were also badly damaged and burned-out cars were strewn nearby.
The suicide bomber was reported to have rammed his explosives-packed vehicle into the gates of the police compound as officers were reporting for inspection, government spokesman Kaloi Akhilgov said. Police fired shots at the truck, but failed to stop it.
"Practically all the cars and buildings in the yard of the police headquarters were completely destroyed," Reuters news agency quoted him as saying.
Mr Akghilov told the AFP news agency that all of the dead were police, but 10 children were among those injured. Many of those hurt were living in residential buildings adjacent to the police station, he said.
Many of the injured were said to be in a serious condition. They were taken to hospitals in Nazran, but Mr Akghilov said the authorities were struggling to cope with the casualties.
"We have not had such an attack for a long time," he said, adding that hospitals did not have enough blood to treat the injured.
Much of the violence in Ingushetia has echoed the continuing unrest in Chechnya, with escalating clashes in the past year between pro-Russian security forces and armed militants.
Human rights activists and opposition politicians in Ingushetia told the BBC last year that the republic was now in a situation of "civil war".
In the most high-profile recent attack, Ingush President Yunus-Bek Yevkurov was severely wounded when a suicide bomber attacked his motorcade in June. He has not yet returned to work but is said to be recovering.
In a statement, he blamed Monday's attack on militants angered by recent security operations along the border with Chechnya.
"It was an attempt to destabilise the situation and sow panic," he said.
Less than a week ago, Ingushetia's construction minister was shot dead by masked gunmen.
That followed the shooting dead of three employees of Russia's emergencies ministry.
In Chechnya, Russian forces were engaged in heavy fighting with separatist rebels until a few years ago, though the fighting has become much less intense recently.
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