An explosive device, made using a 155-mm shell, was planted on a bridge over the Sunzha river, and detonated as the officers' truck passed, Chechnya's Prosecutor General Valery Kuznetsov said.
He said the policemen were part of an Interior Ministry special operation unit on temporary duty in Chechnya, from the west Russian city of Orel.
The prosecutor said investigators are searching for the attackers, and suspect certain individuals of involvement in the attack.
Although authorities have announced that the active phase of the counter-terrorism operation in the North Caucasus is over, violence continues to affect the region.
Through a partial amnesty announced on July 15, following the killing of the region's number one terrorist Shamil Basayev, militants not involved in major atrocities were promised leniency.
A law granting amnesty to militants and servicemen guilty of offenses during the North Caucasus antiterrorism campaign came into force in late September.
More than 300 militants have accepted the surrender offer since its announcement, mainly in Chechnya, according to Nikolai Patrushev, the head of Russia's Federal Security Service (FSB) and the National Antiterrorism Committee.