BAGHDAD -- A series of conflicts with insurgent groups along Iran's borders may be impelling Tehran to back its own allies in Iraq in what it regards as a proxy war with the U.S., according to security experts and officials in the U.S., Iran and Iraq.

Dozens of Iranian officials, members of the security forces and insurgents belonging to Kurdish, Arab Iranian and Baluch groups have died in the fighting in recent years. It now appears to be heating up once again after an unusually cold and snowy winter.

In recent weeks, Iranians have begun the now-routine bombardment of suspected rebel Iranian Kurd positions in northern Iraq, and guerrillas have claimed incursions into northwestern Iran.

Some Iranians blamed Sunni Arab radicals for an explosion Saturday that killed 12 and injured 202 at a gathering where a preacher criticized the Wahhabi form of Islam that inspires Osama bin Laden.