Three people have been killed and two others injured in a blast in Nazran, the capital of Russia's southern province of Ingushetia, which borders Chechnya.
Officials in the province, where violent attacks against police and officials have become more frequent recently, have given conflicting accounts of what had happened.
"The regional prosecutors' office said it was a terrorist attack but the interior ministry ruled this out, saying a car accident caused the blast.
Earlier there had been reports that a Russian-made Lada car packed with explosives was parked next to the cultural centre in the town's centre.
The dead were all police officers.
A series of recent attacks against officials and police, blamed on Islamist rebels, has heightened security fears in Ingushetia.
Earlier this month 2,500 troops were sent to the region to support local security forces.
Security measures became especially tight ahead of 1 September, when school year starts in Russia.
A large school is located next to the scene of the blast.
But the Interior ministry gave its own account of what had happened.
A ministry spokesman said a police jeep collided with the Lada car, which ran on gas, and the gas canister exploded after the collision.
