At least 15 people were killed Tuesday when rebels ambushed and blew up a police vehicle in Chechnya, the southern Russian republic wracked by a separatist insurgency.

The assailants first opened fire on police outside a school in the town of Znamenskoye, Russian news agencies reported. When more security forces arrived at the scene, the attackers destroyed the vehicle, the agencies said.

Most of the dead were police officers, but officials said three were civilians, including two children. Twenty people were wounded, some seriously.

Russian forces and their local allies clash almost daily with Chechen separatists. It is the second such conflict over the past decade in Chechnya, where the fighting has killed as many as 100,000 people.

The area of Chechnya where Tuesday's attack occurred, about 40 miles northwest of the regional capital, Grozny, had been relatively quiet since a May 2003 truck bomb attack on a government compound in Znamenskoye killed 60 people.

"A bloody war has been unleashed against us, a war without any rules," said Alu Alkanov, president of the semiautonomous republic's pro-Moscow government.

A Web site where insurgent statements often appear said that the initial firefight was designed to draw more policemen to the scene and maximize casualties with an explosion. "There were no losses on the Chechen side," the statement said. "The resistance fighters returned to their base without any particular problems."

At a government meeting after the attack, Russian President Vladimir Putin said that "the tragic events in the Nadterechny region show that all we are planning must be done, and must be done quickly."

But an element of pessimism has begun to emerge among some in the Russian government, which has long insisted that it was crushing the rebels and normalizing life in the region.

Putin's special envoy to Chechnya, Dmitry Kozak, warned recently in a report to the president that the mostly Muslim part of southern Russia risked becoming a "macro-region of sociopolitical and economic instability" unless widespread abuse of power by local governing elites was reined in.

"A bloody war has been unleashed," said Chechen President Alu Alkanov.