Russia ? The massive explosion in Nazran, the largest city in Russia’s North Caucasus republic of Ingushetia, could have been designed to destabilize the situation there, the republic’s prosecutor said Saturday.

At least four policemen were killed when a car laden with explosives blew up Friday in downtown Nazran with the force of 20 kilograms of TNT.

“There are two main theories we are working on. It is not ruled out that the crime was directed against police. The second theory is destabilization of the situation in the republic,” Yury Turygin said.