The authorities in Russia's southern republic of Ingushetia say 92 people died in raids by Chechen rebels.
Three days of mourning have been declared in Ingushetia
The Interfax news agency quotes a government minister as saying that more than 60 others were wounded.
Co-ordinated attacks by about 200 heavily armed fighters targeted police and border guard posts near the main Ingush city of Nazran on Monday.
Russian President Vladimir Putin - who flew to the area attacked - has said the guerrillas must be "destroyed".
He said a regiment of interior ministry forces would be stationed permanently in the republic, raising the Kremlin's troop commitment in the region.
The republic has begun three days of official mourning.
Earlier reports after the attacks put the number of dead at around 57.
But on Wednesday, Ingushetian Deputy Prime Minister Bashyr Aushev told Interfax: "These figures are not final and it is possible that the information about the number of dead may change upwards.
"We are now receiving information from law enforcing structures, which should give full details about the number of dead according to their lists."
Mainly Muslim population, ethnically close to the Chechens
Suffers occasional overspill of war in Chechnya
Last major battle between fighters and Russian forces in October 2002
An Ingush policeman told the Associated Press agency that the attacks appeared to have been timed around the changing of the guard at the Kavkaz checkpoint between Chechnya and Ingushetia.
He said the dead included many soldiers as well as police and other law enforcement officials who were shot after being called in to work when an official alert was issued.
The officials were stopped at checkpoints set up by the gunmen, who checked their identification papers before killing them, he said.
At least two rebels are reported to have died in the ensuing gun battles.
Thousands of troops, including reinforcements sent across the border from Chechnya, are involved in the hunt for the rebels. They are being supported by helicopter gunships.
The series of attacks by some 200 fighters was the biggest armed operation by rebels in Ingushetia since fighting broke out between separatists and the Russian authorities in neighbouring Chechnya more than a decade ago.
Last week the Chechen rebel leader, Aslan Maskhadov, warned of impending large-scale attacks.
Moscow is preparing for an August election to replace Kremlin-backed Chechen President Akhmad Kadyrov, who was killed last month in a bomb attack that was seen as a significant blow to Mr Putin's efforts to bring stability to Chechnya.
BBC Moscow correspondent Stephen Dalziel says the latest attacks show the rebels are still a force to be reckoned with.