At least three armed suspects who attacked traffic police in Russia’s North Caucasus on Thursday night have been shot and killed, investigators have said.

The restive region has been the site of frequent attacks on law enforcement officials, including a grenade attack on National Guard troops in Ingushetia last December. Armed attacks have also been staged by separatist insurgents in the republics of Chechnya and Dagestan.

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Four knife-wielding assailants attacked traffic police officers on duty in Nalchik, the capital of the republic of Kabardino-Balkaria, wounding one, Russia’s Investigative Committee said Thursday. Bursts of gunfire can be heard on a video of the incident posted on social media.