Russian soldiers, trying to rout Muslim fighters, are targeting their positions in southern Chechnya with heavy artillery barrages.
They have detained as many as 150 people after conducting house to house searches, a Russian official told AP.
The official, who refused to be named, said five Russian soldiers were killed and a further seven wounded when rebels attacked a camp near the border with Georgia.
A Chechen policeman died after he stepped on a mine on Friday in the capital Grozny.
Another land-mine, that exploded whilst it was being laid near Gudermes, Chechnya’s second largest city, killed two fighters.
In a separate incident, three Russian riot policemen were injured and a fighter killed in an armed clash late on Friday.
With travel severely restricted in Chechnya, tolls given by the fighters and Russian government officials are almost impossible to verify.
The war between the Russians and Chechen fighters has left between 5000 and 12,000 Russian soldiers dead.
Tens of thousands of civilians are also believed to have died since the start of the conflict, the second war between the two sides in a decade.
The increase in fighting comes on the eve of elections that the Kremlin hopes will convince the world that the war in the Caucasus is over.
Russian President Vladimir Putin
with pro-Moscow Chechen leader
Still, the last serious rival to Russia's preferred candidate in the presidential elections was on Thursday banned from standing.
Businessman Malik Saidullayev said the Chechen supreme court ruling was inspired by Kremlin officials who wanted to ensure victory for Akhmad Kadyrov.
A former grand mufti of Chechnya, Kadyrov was appointed by Russia to run the pro-Moscow administration in the North Caucasus republic three years ago.
A survey released this week showed 68% of Chechens do not have faith in the elections. Fifty one percent think Kadyrov will win no matter what.