MOSCOW — Two gunmen shot dead a ruling party official on Tuesday in Russia's North Caucasus, where the Kremlin is fighting to subdue an Islamist insurgency, investigators said.

Unknown assailants burst into Boris Zherukov's office in Nalchik, capital of the province of Kabardino-Balkaria, and shot him twice in the head, Russia's Investigative Committee said in a statement.

Zherukov was head of President Vladimir Putin's ruling United Russia party faction in the local parliament. He was also rector of the local State Agricultural University.

Insurgents fighting to carve an Islamic state out of a patchwork of mainly Muslim regions in Russia's mountainous south stage near-daily shootings and bomb attacks targeting officials and police.

The violence — fueled by discontent over joblessness, corruption, and police brutality — is mostly limited to the North Caucasus, where the Kremlin fought two wars against separatist rebels in Chechnya since the 1991 collapse of the Soviet Union.

But insurgents have also struck the Russian heartland, claiming responsibility for a suicide bombing that killed 37 at Moscow's busiest airport in 2011 and twin bombings on the Moscow metro that killed 40 in 2010.