Iran, which has forecfully cracked down on anti-regime protesters in its own county in recent weeks, denounced the arrival of Saudi troops in Bahrain on Tuesday, arguing, in the words of an Iranian Foreign Ministry spokesman, that foreign "interference and increasing suppression and violent confrontation is not the solution to the legitimate demands of the [Bahraini] people."

The six-nation Gulf Cooperation Council (GCC) is sending forces--including around 1,000 Saudi soldiers--into Bahrain to maintain order and secure government facilities in the face of increasingly violent anti-government protests, which have prompted the country's king to declare a state of emergency. The GCC action represent the "first major cross-border action against the revolts that have erupted across the Arab world," according to the Associated Press, and is motivated in part by a desire to keep the unrest in Bahrain from spreading to its neighbors.

What explains Iran's stance? Sunni-Shiite regional schisms, Reuters suggests. Bahrain's protesters, drawn largely from the country's Shiite majority, are demonstrating against what they perceive as discrimination by the country's Sunni monarchy. Iran, the main Shiite power in a Gulf region where most ruling families--including Saudi Arabia's--are Sunni Muslims, is therefore alarmed by Saudi Arabia's decision to send troops into Bahrain. "Iran holds no deep political ties to Bahrain's Shiite groups," the AP explains, "but some Iranian hard-liners in the past have hailed their efforts for greater rights." Sunni-ruled Gulf states, meanwhile, worry that "gains by Bahrain's Shiite Muslims could offer a window for Shiite power Iran to expand its influence on the Arab side of the Gulf."

It's unclear how much trouble Saudi Arabia-Iran standoff spells for the region. The Saudi action, Reuters explains, could escalate tensions with its fellow oil exporter Iran "to dangerous levels. But the Iranian Foreign Ministry spokesman on Tuesday dismissed the idea of Iran sending forces into Bahrain, and Iran has also denied rumors that it's secretly backing Bahraini protesters. 

The Saudi intervention in Bahrain has already turned deadly; the AP is reporting that  a Saudi soldier was shot dead on Tuesday by an opposition protester in the country's capital, Manama. "If true," the AP says, "it would mark a dramatic shift in the tactics by the opposition," which has so far remained peaceful.