Five police officers have been killed by a roadside bomb in Grozny, the capital of the Russian republic of Chechnya, officials have said.
The officers were working on security ahead of the inauguration of Russia's president-elect Dmitry Medvedev.
Major fighting between Chechen rebels and Russian forces has died down in recent years but hit and run attacks on security forces have continued.
The attack, late on Sunday, is the most lethal in many months.
Two wars
Police officials said the bomb was detonated by remote control at a police checkpoint.
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Police investigate at the scene of the explosion
"According to provisional information, the device was home-made, as nuts, bolts and ball bearings were found at the scene," Grozny police spokesman Ramzan Edilov told AFP news agency.
"The search for the criminals is under way, they will be found and liquidated," he said.
Russian forces stormed into Chechnya to crush a separatist revolt in December 1994.
Large-scale military operations were resumed in 1999, when Vladimir Putin was prime minister, but in recent years large-scale fighting has died down.
Mr Medvedev won a landslide victory to succeed Vladimir Putin as Russian president in March, and is due to be sworn in on Wednesday.
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