Two carloads of assailants attacked a hydroelectric station in southern Russia early Wednesday, killing two workers and setting off bombs.

The attack took place in Kabardino-Balkariya, one of the republics in Russia's restive Caucasus region where clashes with insurgents are frequent.

A spokesman for the republic's police, Adlan Kakakuyev, said two cars carrying a half-dozen assailants attacked the Baksan plant at about 4:30 a.m., killing two guards and wounding three others in gunfire. The attackers then set off explosives in several parts of the 25-megawatt plant and detonated them before fleeing.

There were no immediate claims of responsibility for the attack.

The explosions and subsequent fire destroyed two of the plant's three power units, but there was no danger of flooding downriver, the state news agency ITAR-Tass cited power company RusGidro as saying. The dam and plant are on the Baksan River, a waterway that flows into the Terek, a major regional river.

Kakakuyev said the same attackers are believed to have earlier opened fire on a police station in the town of Baksan. No one was hurt in that attack.

The attack on the hydroelectric station was the most dramatic outburst of violence in the Russian Caucasus in recent months. Although Kabardino-Balkariya sees less violence than nearby Chechnya, Dagestan and Ingushetia, the republic suffers from persistent tensions stemming from poverty and harsh police actions toward worship by unsanctioned Muslim sects.

In October 2005, dozens of men stormed the capital city, Nalchik, attacking police and government offices. Some 139 people died, including 94 militants.

Wednesday's attack did not cause power outages, according to Russian news reports. The plant produces only about 7 percent of the electricity consumed in Kabardino-Bakariya and other plants were able to make up for the loss.

Although the plant has comparatively minor strategic value, the attacked demonstrated how regional militants continue to be capable of mounting bold assaults despite years of anti-terrorist efforts by police and the military.