Fourteen people have been killed and more than 20 injured in an explosion in Chechnya, reports from Russia say.
Police and civilians died when the vehicle exploded
Officials said a police car was shot at and blown up in Znamenskoye, 60km (37 miles) north of the capital, Grozny.
Chechen President Alu Alkhanov has blamed the attack on separatist rebels led by Shamil Basayev, Russian news agency Itar-Tass reports.
Russia's President Vladimir Putin has ordered an acceleration of plans to tighten borders in the region, it adds.
Tuesday's incident happened in Chechnya's north western Nadterechny district, usually considered to be under the control of Russian security forces.
Mr Putin told his government that plans to reinforce troops along Russia's volatile southern Caucasus border must be implemented "as quickly as possible".
Meanwhile, security forces have begun the hunt for those responsible for the explosion at about 1330 (0930 GMT) in Znamenskoye.
Local police said attackers in a car had at first opened fire on a police vehicle near a school, then detonated explosives when reinforcements arrived, Itar-Tass reports.
Chechnya's Prime Minister Sergei Abramov told the agency 11 police officers and three civilians had been killed, among them two teenagers and a local police chief.
About 24 wounded have been flown to the nearest hospitals for treatment - some with serious injuries, Russian news agency Interfax said.
The Chechen Interior Ministry told Itar-Tass the attack had been targeted against police officers.
Chechen President Alu Alkhanov said he had evidence those involved had been working for Chechen warlord Basayev, who claimed responsibility for last year's Beslan school siege.
"No statute of limitations applies to this crime. Its organisers and those who carried it out will not escape retribution," Itar-Tass quotes Mr Alkhanov as saying.
Correspondents say that although Russian forces control most of Chechnya, isolated rebel attacks have continued and even spread to neighbouring regions.
Mr Putin last week visited the southern Russian region of Dagestan, where he urged ministers and commanders to take action to halt violence.
At least 10 people were killed in a bomb attack on a truck carrying security forces near the Dagestani capital, Makhachkala, earlier this month.
In 2003, a truck bomb outside a government compound in Znamenskoye killed at least 60 people and injured many more.