"Four military personnel were injured as a result of an explosion in the town of Karabulak. All of them have been hospitalized, one of them in a grave condition," the representative of the Investigation Committee of the Ingush Prosecutor General's Office said
A police source said the blast occurred when a remote-controlled explosive device was set off as a patrol of Interior Ministry's troops was passing by.
An investigation into the incident is underway.
Ingushetia, which borders Chechnya, has seen a rise in violence in recent months. The Russia-based human rights organization, the Moscow Helsinki Group, said in late September that the republic was on the verge of civil war as fighting between militants and authorities intensified.