In the last month, the war between Iran and Kurdish separatists has escalated. Over thirty people have died, and, for the first time, Iran used airpower (three armed helicopters) to raid a village in Iraq that was used as a base for Iranian Kurd rebels.
Iran and Iraq have been fighting a low level war with Kurds since the end of World War I. Back then, the Ottoman Turk empire, which had long controlled what is now Iraq, collapsed. Iraq was created, and the Kurds got the idea that this was their time to become united and form their own country (Kurdistan). It was not to be. The Kurdish population remained split, living in Turkey (the heartland of the Ottoman empire), Iraq, Iran and Syria. Most of the four million Iranian Kurds are Sunni Moslems, while Iran is run by Shia clergy. So the violence is religious, as well as ethnic and political.
In the 1970s, Iran and Iraq agreed to not give sanctuary to Kurdish separatists. This made it easier for both countries to crush such movements, since sanctuary across the border was no longer possible. But around the same time, a new group, the PKK (Kurdistan Workers' Party) arose in Turkey, and it took three decades, and 30,000 dead, to suppress them. But the PKK is not destroyed, and still survives in northern Iraq sanctuaries. Turkey regularly raids these PKK bases in Iraq, and the Iraqis tolerate it (the only other option is war with Turkey, which no Arab nations believes is a sane move.)
In effect, the Iranians are doing the same thing the Turks have been doing for over a decade. The Iranian Kurdish rebels have their own organization, the PJAK (Party of Free Life of Kurdistan), which is allied with the PKK. Up until now, the Iranians have held back from actually going into Iraq, fearing that this would give the Americans an excuse to attack Iran. Apparently this is no longer a problem, and is most likely because the Iranians have been more willing to cooperate with Afghanistan in fighting the Taliban.
Some of the more radical factions in the Iranian government had long supported the Taliban, mainly because the Taliban were fighting the Americans. But most Iranians are anti-Taliban, because the Taliban is a radical Sunni Arab group that has killed thousands of Shia Afghans. The Kurds, while mostly Sunni, have been less about religion (the PKK and PJAK are largely secular) and more about ethnicity.