Nalchik was on high alert Sunday after militants fired on the local Federal Security Service's headquarters, an FSB-owned sanatorium and two traffic police checkpoints, injuring one police officer.
The attack in the capital of the Kabardino-Balkaria republic was coordinated by three groups of militants at about 8 p.m. Friday, said a police source, speaking on condition of anonymity.
One group of attackers launched three grenades at the FSB building in downtown Nalchik, a spokesman for investigators told Interfax. "There were three shots from a grenade launcher," the spokesman said. "The shells fell on the second and seventh floors of the building. None of the staff was hurt."
The grenades were launched from a nearby children's park, investigators said.
About the same time, a grenade was thrown onto the grounds of the Leningrad sanatorium run by the FSB. The explosion caused no injuries.
Two traffic police checkpoints also came under fire in Nalchik, and one officer was injured, Interfax said.
The attacks are the latest blow to Kremlin efforts to contain a swelling insurgency in the North Caucasus, a decade after federal forces threw separatists out of power in the second separatist war in Chechnya.
Rebels angry about poverty and fueled by religious fervor want to carve out a separate Islamic state and install sharia law. They said they ordered the attack on Moscow's Domodedovo Airport last month that killed 37 people.
They also claimed responsibility for shooting dead three Moscow tourists a week ago in Kabardino-Balkaria, who were going to ski on Mount Elbrus, Europe's highest peak.
Violence in Kabardino-Balkaria has increased over the last year, leading analysts to say the insurgency is expanding beyond its usual centers of violence, such as Dagestan and Chechnya.
Though the Kremlin continues to pour billions of dollars into the North Caucasus, analysts say this has little effect and violence will continue to rise.
In a 2005 attack on Nalchik, 139 people were killed, including 94 militants.
(Reuters, MT, AP)